Classes
You are encouraged to solve this task according to the task description, using any language you may know.
In object-oriented programming class is a set (a transitive closure) of types bound by the relation of inheritance. It is said that all types derived from some base type T and the type T itself form a class T.
The first type T from the class T sometimes is called the root type of the class.
A class of types itself, as a type, has the values and operations of its own. The operations of are usually called methods of the root type. Both operations and values are called polymorphic.
A polymorphic operation (method) selects an implementation depending on the actual specific type of the polymorphic argument.
The action of choice the type-specific implementation of a polymorphic operation is called dispatch. Correspondingly, polymorphic operations are often called dispatching or virtual. Operations with multiple arguments and/or the results of the class are called multi-methods. A further generalization of is the operation with arguments and/or results from different classes.
- single-dispatch languages are those that allow only one argument or result to control the dispatch. Usually it is the first parameter, often hidden, so that a prefix notation x.f() is used instead of mathematical f(x).
- multiple-dispatch languages allow many arguments and/or results to control the dispatch.
A polymorphic value has a type tag indicating its specific type from the class and the corresponding specific value of that type.
This type is sometimes called the most specific type of a [polymorphic] value.
The type tag of the value is used in order to resolve the dispatch.
The set of polymorphic values of a class is a transitive closure of the sets of values of all types from that class.
In many OO languages the type of the class of T and T itself are considered equivalent. In some languages they are distinct (like in Ada). When class T and T are equivalent, there is no way to distinguish polymorphic and specific values.
- Task
Create a basic class with a method, a constructor, an instance variable and how to instantiate it.
11l
<lang 11l>T MyType
Int public_variable // member variable = instance variable . Int private_variable
F () // constructor
.private_variable = 0
F someMethod() // member function = method
.private_variable = 1
.public_variable = 10</lang>
Note that member functions in 11l by default are not polymorphic; if you want a polymorphic member function, you have to mark it as virtual. Example: <lang 11l>T MyType
F.virtual.new someMethod() -> N // this is polymorphic
print()</lang>
ActionScript
<lang actionscript>package {
public class MyClass {
private var myVariable:int; // Note: instance variables are usually "private"
/**
* The constructor
*/
public function MyClass() {
// creates a new instance
}
/**
* A method
*/
public function someMethod():void {
this.myVariable = 1; // Note: "this." is optional
// myVariable = 1; works also
}
}
}</lang>
Ada
Class is used in many languages to provide both encapsulation, or grouping of data and actions, and type definition. Ada packages provide encapsulation or grouping while type definitions are done using the type reserved word. Types participating in inheritance are named tagged record types.
A package specification has the following form: <lang ada>package My_Package is
type My_Type is tagged private; procedure Some_Procedure(Item : out My_Type); function Set(Value : in Integer) return My_Type;
private
type My_Type is tagged record
Variable : Integer := -12;
end record;
end My_Package;</lang> The type declaration at the top of the package gives public visibility to the private tagged type My_Type. Since My_Type is declared to be private, the public has no visibility of its structure. The type must be treated as a black box. The private section of the package specification includes the actual tagged record definition. Note that the data member Variable is initialized to -12. This corresponds to a default constructor for the type.
The package body must contain the implementation of the procedures and functions declared in the package specification. <lang ada> package body My_Package is
procedure Some_Procedure(Item : out My_Type) is
begin
Item := 2 * Item;
end Some_Procedure;
function Set(Value : Integer) return My_Type is
Temp : My_Type;
begin
Temp.Variable := Value;
return Temp;
end Set;
end My_Package;</lang> The Set function acts as a conversion constructor for My_Type.
An instance is typically created outside the package: <lang ada>with My_Package; use My_Package;
procedure Main is
Foo : My_Type; -- Foo is created and initialized to -12
begin
Some_Procedure(Foo); -- Foo is doubled Foo := Set(2007); -- Foo.Variable is set to 2007
end Main;</lang>
Aikido
Aikido provides classes with single inheritance and multiple interface implementation. A class takes a set of constructor arguments and provides a set of public functions, operators, classes, monitors and threads. <lang aikido>class Circle (radius, x, y) extends Shape (x, y) implements Drawable {
var myvec = new Vector (x, y)
public function draw() {
// draw the circle
}
}</lang>
ALGOL 68
The following code is experimental. Basically ALGOL 68 is not object oriented, so the task to create (and use of) objects is tedious due to the lack of certain constructs, especially the lack of OO syntactic sugar.
For further details:
Other examples of this experimental approach are located at pages: Life in two dimensions, Playing Cards and Stack.
<lang algol68>MODE MYDATA = STRUCT(
INT name1
); STRUCT(
INT name2, PROC (REF MYDATA)REF MYDATA new, PROC (REF MYDATA)VOID init, PROC (REF MYDATA)VOID some method
) class my data; class my data := (
# name2 := # 2, # Class attribute #
# PROC new := # (REF MYDATA new)REF MYDATA:(
(init OF class my data)(new);
new
),
# PROC init := # (REF MYDATA self)VOID:(
""" Constructor (Technically an initializer rather than a true 'constructor') """;
name1 OF self := 0 # Instance attribute #
),
# PROC some method := # (REF MYDATA self)VOID:(
""" Method """;
name1 OF self := 1;
name2 OF class my data := 3
)
);
- class name, invoked as a function is the constructor syntax #
REF MYDATA my data = (new OF class my data)(LOC MYDATA);
MODE GENDEROPT = UNION(STRING, VOID); MODE AGEOPT = UNION(INT, VOID);
MODE MYOTHERDATA = STRUCT(
STRING name, GENDEROPT gender, AGEOPT age
); STRUCT (
INT count, PROC (REF MYOTHERDATA, STRING, GENDEROPT, AGEOPT)REF MYOTHERDATA new, PROC (REF MYOTHERDATA, STRING, GENDEROPT, AGEOPT)VOID init, PROC (REF MYOTHERDATA)VOID del
) class my other data; class my other data := (
# count := # 0, # Population of "(init OF class my other data)" objects #
- PROC new := # (REF MYOTHERDATA new, STRING name, GENDEROPT gender, AGEOPT age)REF MYOTHERDATA:(
(init OF class my other data)(new, name, gender, age);
new
),
# PROC init := # (REF MYOTHERDATA self, STRING name, GENDEROPT gender, AGEOPT age)VOID:(
""" One initializer required, others are optional (with different defaults) """;
count OF class my other data +:= 1;
name OF self := name;
gender OF self := gender;
CASE gender OF self IN
(VOID):gender OF self := "Male"
ESAC;
age OF self := age
),
# PROC del := # (REF MYOTHERDATA self)VOID:(
count OF class my other data -:= 1
)
);
PROC attribute error := STRING: error char; # mend the error with the "error char" #
- Allocate the instance from HEAP #
REF MYOTHERDATA person1 = (new OF class my other data)(HEAP MYOTHERDATA, "John", EMPTY, EMPTY); print (((name OF person1), ": ",
(gender OF person1|(STRING gender):gender|attribute error), " ")); # "John Male" #
print (((age OF person1|(INT age):age|attribute error), new line)); # Raises AttributeError exception! #
- Allocate the instance from LOC (stack) #
REF MYOTHERDATA person2 = (new OF class my other data)(LOC MYOTHERDATA, "Jane", "Female", 23); print (((name OF person2), ": ",
(gender OF person2|(STRING gender):gender|attribute error), " "));
print (((age OF person2|(INT age):age|attribute error), new line)) # "Jane Female 23" #</lang>
- Output:
John: Male * Jane: Female +23
AmigaE
<lang amigae>OBJECT a_class
varA, varP
ENDOBJECT
-> this could be used like a constructor PROC init() OF a_class
self.varP := 10 self.varA := 2
ENDPROC
-> the special proc end() is for destructor PROC end() OF a_class -> nothing to do here... ENDPROC
-> a not so useful getter PROC getP() OF a_class IS self.varP
PROC main()
DEF obj : PTR TO a_class
NEW obj.init()
WriteF('\d\n', obj.varA) -> this can be done, while
-> varP can't be accessed directly
WriteF('\d\n', obj.varP) -> or
WriteF('\d\n', obj.getP())
END obj
ENDPROC</lang>
AutoHotkey
AutoHotkey_L is prototype-based. However, for convenience, class-syntax may be used to create a base object. <lang AutoHotkey>obj := new MyClass obj.WhenCreated()
class MyClass {
- Instance Variable #1
time := A_Hour ":" A_Min ":" A_Sec
- Constructor
__New() {
MsgBox, % "Constructing new object of type: " this.__Class
FormatTime, date, , MM/dd/yyyy
; Instance Variable #2
this.date := date
}
- Method
WhenCreated() {
MsgBox, % "Object created at " this.time " on " this.date
}
}</lang>
BaCon
This is an advanced feature to extend the the compiler we can also compile using g++ or clang++ using PRAGMA
<lang cpp> PRAGMA COMPILER g++ PRAGMA OPTIONS -Wno-write-strings -Wno-pointer-arith -fpermissive
OPTION PARSE FALSE
'---The class does the declaring for you
CLASS Books public: const char* title; const char* author; const char* subject; int book_id; END CLASS
'---pointer to an object declaration (we use a class called Books)
DECLARE Book1 TYPE Books
'--- the correct syntax for class
Book1 = Books()
'--- initialize the strings const char* in c++
Book1.title = "C++ Programming to bacon "
Book1.author = "anyone"
Book1.subject ="RECORD Tutorial"
Book1.book_id = 1234567
PRINT "Book title : " ,Book1.title FORMAT "%s%s\n"
PRINT "Book author : ", Book1.author FORMAT "%s%s\n"
PRINT "Book subject : ", Book1.subject FORMAT "%s%s\n"
PRINT "Book book_id : ", Book1.book_id FORMAT "%s%d\n"
</lang>
Now the same but using the c++ "new" command and arrow operators syntax
<lang cpp> PRAGMA COMPILER g++ PRAGMA OPTIONS -Wno-write-strings -Wno-pointer-arith -fpermissive
OPTION PARSE FALSE
'---The class does the declaring for you
CLASS Books public: const char* title; const char* author; const char* subject; int book_id; END CLASS
'---pointer to an object declaration (we use a class called Books)
DECLARE Book1 TYPE Books*
'--- the correct syntax for class
Book1 = new Books()
'--- initialize the strings const char* in c++
Book1->title = "C++ Programming to bacon "
Book1->author = "anyone"
Book1->subject ="RECORD Tutorial"
Book1->book_id = 1234567
PRINT "Book title : " ,Book1->title FORMAT "%s%s\n"
PRINT "Book author : ", Book1->author FORMAT "%s%s\n"
PRINT "Book subject : ", Book1->subject FORMAT "%s%s\n"
PRINT "Book book_id : ", Book1->book_id FORMAT "%s%d\n"
</lang>
BASIC
<lang basic> DECLARE SUB MyClassDelete (pthis AS MyClass)
DECLARE SUB MyClassSomeMethod (pthis AS MyClass) DECLARE SUB MyClassInit (pthis AS MyClass)
TYPE MyClass Variable AS INTEGER END TYPE
DIM obj AS MyClass MyClassInit obj MyClassSomeMethod obj
SUB MyClassInit (pthis AS MyClass) pthis.Variable = 0 END SUB
SUB MyClassSomeMethod (pthis AS MyClass) pthis.Variable = 1 END SUB</lang>
BBC BASIC
<lang bbcbasic> INSTALL @lib$+"CLASSLIB"
REM Declare the class:
DIM MyClass{variable, @constructor, _method}
DEF MyClass.@constructor MyClass.variable = PI : ENDPROC
DEF MyClass._method = MyClass.variable ^ 2
REM Register the class:
PROC_class(MyClass{})
REM Instantiate the class:
PROC_new(myclass{}, MyClass{})
REM Call the method:
PRINT FN(myclass._method)
REM Discard the instance:
PROC_discard(myclass{})</lang>
blz
<lang blz>
- Constructors can take parameters (that automatically become properties)
constructor Ball(color, radius)
# Objects can also have functions (closures) :volume return 4/3 * {pi} * (radius ** 3) end :show return "a " + color + " ball with radius " + radius end
end
red_ball = Ball("red", 2) print(red_ball)
- => a red ball with radius 2
</lang>
Bracmat
Bracmat has no class-inheritance. Any object can function as a template for creating other objects. <lang bracmat>( ( resolution
= (x=)
(y=)
(new=.!arg:(?(its.x),?(its.y)))
)
& new$(resolution,640,480):?VGA & new$(resolution,1920,1080):?1080p & out$("VGA: horizontal " !(VGA..x) " vertical " !(VGA..y)));</lang>
- Output:
VGA: horizontal 640 vertical 480
C
<lang c>
- include <stdlib.h>
typedef struct sMyClass {
int variable;
} *MyClass;
MyClass MyClass_new() {
MyClass pthis = malloc(sizeof *pthis); pthis->variable = 0; return pthis;
}
void MyClass_delete(MyClass* pthis) {
if (pthis)
{
free(*pthis);
*pthis = NULL;
}
}
void MyClass_someMethod(MyClass pthis) {
pthis->variable = 1;
}
MyClass obj = MyClass_new(); MyClass_someMethod(obj); MyClass_delete(&obj);</lang>
C#
<lang csharp>public class MyClass {
public MyClass()
{
}
public void SomeMethod()
{
}
private int _variable;
public int Variable
{
get { return _variable; }
set { _variable = value; }
}
public static void Main()
{
// instantiate it
MyClass instance = new MyClass();
// invoke the method
instance.SomeMethod();
// set the variable
instance.Variable = 99;
// get the variable
System.Console.WriteLine( "Variable=" + instance.Variable.ToString() );
}
}</lang>
C++
<lang cpp>class MyClass { public:
void someMethod(); // member function = method MyClass(); // constructor
private:
int variable; // member variable = instance variable
};
// implementation of constructor MyClass::MyClass():
variable(0)
{
// here could be more code
}
// implementation of member function void MyClass::someMethod() {
variable = 1; // alternatively: this->variable = 1
}
// Create an instance as variable MyClass instance;
// Create an instance on free store MyClass* pInstance = new MyClass; // Instances allocated with new must be explicitly destroyed when not needed any more: delete pInstance;</lang>
Note: MyClass instance(); would not define an instance, but declare a function returning an instance. Accidentally declaring functions when object definitions are wanted is a rather common bug in C++.
Functions can also be defined inline:
<lang cpp>class MyClass { public:
MyClass(): variable(0) {}
void someMethod() { variable = 1; }
private:
int variable;
};</lang>
Note that member functions in C++ by default are not polymorphic; if you want a polymorphic member function, you have to mark it as virtual. In that case, you should also add a virtual destructor, even if that is empty. Example:
<lang cpp>class MyClass { public:
virtual void someMethod(); // this is polymorphic virtual ~MyClass(); // destructor
};</lang>
Clojure
Clojure gives you several options, and to help you decide which is more appropriate to use, see the Clojure type selection flowchart.
defrecord example: <lang clojure>
- You can think of this as an interface
(defprotocol Foo (getFoo [this]))
- Generates Example1 Class with foo as field, with method that returns foo.
(defrecord Example1 [foo] Foo (getFoo [this] foo))
- Create instance and invoke our method to return field value
(-> (Example1. "Hi") .getFoo) "Hi"</lang>
COBOL
<lang cobol> IDENTIFICATION DIVISION.
CLASS-ID. my-class INHERITS base.
*> The 'INHERITS base' and the following ENVIRONMENT DIVISION
*> are optional (in Visual COBOL).
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
REPOSITORY.
CLASS base.
*> There is no way (as far as I can tell) of creating a
*> constructor. However, you could wrap it with another
*> method to achieve the desired effect.
*>...
OBJECT.
*> Instance data
DATA DIVISION.
WORKING-STORAGE SECTION.
01 instance-variable PIC 9(8).
*> Properties can have getters and setters automatically
*> generated.
01 a-property PIC 9(8) PROPERTY.
PROCEDURE DIVISION.
METHOD-ID. some-method.
PROCEDURE DIVISION.
*> ...
END METHOD some-method.
END OBJECT.
END CLASS my-class.
IDENTIFICATION DIVISION.
PROGRAM-ID. example-class-use.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
REPOSITORY.
*> These declarations brings the class and property into
*> scope.
CLASS my-class
PROPERTY a-property.
DATA DIVISION.
WORKING-STORAGE SECTION.
*> Declaring a my-class reference variable.
01 instance USAGE OBJECT REFERENCE my-class.
PROCEDURE DIVISION.
*> Invoking a static method or (in this case) a constructor.
INVOKE my-class "new" RETURNING instance
*> Invoking an instance method.
INVOKE instance "some-method"
*> Using the setter and getter of a-property.
MOVE 5 TO a-property OF instance
DISPLAY a-property OF instance
GOBACK
.
END PROGRAM example-class-use.</lang>
Coco
<lang coco>class Rectangle
# The constructor is defined as a bare function. This # constructor accepts one argument and automatically assigns it # to an instance variable. (@width) -> # Another instance variable. length: 10 # A method. area: -> @width * @length
- Instantiate the class using the 'new' operator.
rect = new Rectangle 2</lang>
CoffeeScript
<lang coffeescript># Create a basic class class Rectangle
# Constructor that accepts one argument constructor: (@width) -> # An instance variable length: 10 # A method area: () -> @width * @length
- Instantiate the class using the new operator
rect = new Rectangle 2</lang>
Common Lisp
<lang lisp>(defclass circle ()
((radius :initarg :radius
:initform 1.0
:type number
:reader radius)))
(defmethod area ((shape circle))
(* pi (expt (radius shape) 2)))
> (defvar *c* (make-instance 'circle :radius 2)) > (area *c*) 12.566370614359172d0</lang>
Component Pascal
BlackBox Component Builder
Module that defines a Class <lang oberon2> MODULE Point; IMPORT Strings; TYPE Instance* = POINTER TO LIMITED RECORD x-, y- : LONGINT; (* Instance variables *) END;
PROCEDURE (self: Instance) Initialize*(x,y: LONGINT), NEW; BEGIN self.x := x; self.y := y END Initialize;
(* constructor *) PROCEDURE New*(x, y: LONGINT): Instance; VAR point: Instance; BEGIN NEW(point); point.Initialize(x,y); RETURN point END New;
(* methods *) PROCEDURE (self: Instance) Add*(other: Instance): Instance, NEW; BEGIN RETURN New(self.x + other.x,self.y + other.y); END Add;
PROCEDURE (self: Instance) ToString*(): POINTER TO ARRAY OF CHAR, NEW; VAR xStr,yStr: ARRAY 64 OF CHAR; str: POINTER TO ARRAY OF CHAR; BEGIN Strings.IntToString(self.x,xStr); Strings.IntToString(self.y,yStr); NEW(str,128);str^ := "@(" +xStr$ + "," + yStr$ + ")"; RETURN str END ToString; END Point. </lang> Module that uses previous class <lang oberon2> MODULE DrivePoint; IMPORT Point, StdLog;
PROCEDURE Do*; VAR p,q: Point.Instance; BEGIN p := Point.New(1,2); q := Point.New(2,1); StdLog.String(p.ToString() + " + " + q.ToString() + " = " + p.Add(q).ToString());StdLog.Ln; StdLog.String("p.x:> ");StdLog.Int(p.x);StdLog.Ln; StdLog.String("p.y:> ");StdLog.Int(p.y);StdLog.Ln END Do;
END DrivePoint.
</lang>
Execute: ^Q DrivePoint.Do
- Output:
@(1,2) + @(2,1) = @(3,3) p.x:> 1 p.y:> 2
Crystal
<lang crystal>class MyClass
def initialize @instance_var = 0 end def add_1 @instance_var += 1 end
end
my_class = MyClass.new </lang>
D
<lang d>import std.stdio;
class MyClass {
//constructor (not necessary if empty)
this() {}
void someMethod() {
variable = 1;
}
// getter method
@property int variable() const {
return variable_;
}
// setter method
@property int variable(int newVariable) {
return variable_ = newVariable;
}
private int variable_;
}
void main() {
// On default class instances are allocated on the heap // The GC will manage their lifetime auto obj = new MyClass();
// prints 'variable = 0', ints are initialized to 0 by default
writeln("variable = ", obj.variable);
// invoke the method obj.someMethod();
// prints 'variable = 1'
writeln("variable = ", obj.variable);
// set the variable using setter method obj.variable = 99;
// prints 'variable = 99'
writeln("variable = ", obj.variable);
}</lang>
Delphi
<lang Delphi>program SampleClass;
{$APPTYPE CONSOLE}
type
TMyClass = class private FSomeField: Integer; // by convention, fields are usually private and exposed as properties public constructor Create; destructor Destroy; override; procedure SomeMethod; property SomeField: Integer read FSomeField write FSomeField; end;
constructor TMyClass.Create; begin
FSomeField := -1
end;
destructor TMyClass.Destroy; begin
// free resources, etc
inherited Destroy;
end;
procedure TMyClass.SomeMethod; begin
// do something
end;
var
lMyClass: TMyClass;
begin
lMyClass := TMyClass.Create; try lMyClass.SomeField := 99; lMyClass.SomeMethod(); finally lMyClass.Free; end;
end.</lang>
DM
In DM, all "classes" are part of the "object tree". Instance variables, procs (functions), ... are all defined inside this "tree". Adding elements (procs, variables, classes) to this tree is done by defining the name and such.
<lang DM>s</lang>
This declares a type "/s" at the root of the tree, which can now be instantiated.
A more complicated example:
<lang DM> // Declare the class "/foo" foo
// Everything inside the indented block is relative to the parent, "/foo" here. // Instance variable "bar", with a default value of 0 // Here, var/bar is relative to /foo, thus it becomes "/foo/var/bar" ultimately. var/bar = 0
// The "New" proc is the constructor.
New()
// Constructor code.
// Declares a proc called "Baz" on /foo
proc/baz()
// Do things.
// Instantiation code. // Overriding /client/New() means it is ran when a client connects. /client/New()
..() var/foo/x = new /foo() x.bar = 10 // Assign to the instance variable. x.baz() // Call "baz" on our instance.
</lang>
This is enough to declare a
Dragon
<lang dragon>class run{ func val(){ showln 10+20 } } </lang>
DWScript
Methods can be implemented inline or out-of-line, this sample illustrates both. <lang Delphi>type
TMyClass = class
private
FSomeField: Integer; // by convention, fields are usually private and exposed as properties
public
constructor Create;
begin
FSomeField := -1;
end;
procedure SomeMethod;
property SomeField: Integer read FSomeField write FSomeField;
end;
procedure TMyClass.SomeMethod; begin
// do something
end;
var lMyClass: TMyClass;
lMyClass := new TMyClass; // can also use TMyClass.Create
lMyClass.SomeField := 99; lMyClass.SomeMethod;</lang>
E
In E, classes, constructors, and instance variables are not built into the language. This is an example of the basic convention; different cases may call for objects built in different ways.
<lang e>def makeColor(name :String) {
def color {
to colorize(thing :String) {
return `$name $thing`
}
}
return color
}</lang>
Example interactive session creating and using it:
<lang e>? def red := makeColor("red")
- value: <color>
? red.colorize("apple")
- value: "red apple"</lang>
EchoLisp
<lang lisp> (lib 'gloops) ; load oo library
(define-class Person null (name (age :initform 66))) (define-method tostring (Person) (lambda (p) ( format "🚶 %a " p.name))) (define-method mailto (Person Person) (lambda( p o) (printf "From %a to️ %a : ..." p o)))
- define a sub-class of Person with same methods
(define-class Writer (Person) (books)) (define-method tostring (Writer) (lambda (w)( format "🎩 %a" w.name))) (define-method mailto (Person Writer) (lambda (p w) (printf " From %a (age %d). Dear writer of %a ..." p p.age w.books )))
</lang>
- Output:
<lang lisp>
- instantiate
(define simone (make-instance Person :name 'simone :age 42)) ;; slots values by name (define antoinette (make-instance Person :name 'antoinette :age 37)) (define albert (Person "albert" 33)) ;; quick way : slots values in order (define simon (make-instance Writer :name "simon" :books '(my-life my-bike)))
(mailto simone simon) ;; method Person-Writer
(mailto simone antoinette) ;; method Person-Person
(mailto simon albert) ;; no method Writer-Person : call 'super' Person-Person
(mailto simon simon) ;; no mehod Writer-Writer : call 'super' Person-Writer
→ From 🚶 simone (age 42). Dear writer of (my-life my-bike) ... From 🚶 simone to️ 🚶 antoinette : ... From 🎩 simon to️ 🚶 albert : ... From 🎩 simon (age 66). Dear writer of (my-life my-bike) ...
</lang>
Eiffel
The Most Basic Form of Class
The shortest way to write an Eiffel class is to have the class keyword, followed by the name of the class (all caps), and ending with the end keyword. <lang Eiffel> class MY_CLASS end </lang>
Add a Creation Procedure (Constructor)
<lang Eiffel> class MY_CLASS
create
make
feature {NONE} -- Initialization
make
-- This is a creation procedure or "Constructor".
do
create my_string.make_empty
end
end </lang>
Add Multiple Creation Procedures (Constructors)
In Eiffel, you may have more than one creation procedure (or "Constructor"). <lang Eiffel> class MY_CLASS
create -- Here we are declaring ...
make, -- In the Feature group (below) we are coding make_this_way, -- each of these declared creation procedures. make_that_way, -- We can have as many constructors as we need. make_another_way, a_name_other_than_make
feature {NONE} -- Initialization
make
-- This is a creation procedure or "Constructor".
do
-- Initialization code goes here ...
end
make_this_way
-- Make this way, rather than a plain ole "make".
do
-- Initialization code goes here ...
end
make_that_way
-- Create that way rather than this way (above).
do
-- Initialization code goes here ...
end
make_another_way
-- And still another way to create MY_CLASS.
do
-- Initialization code goes here ...
end
a_name_other_than_make
-- There is no requirement to use the word "make".
-- The word "make" is just a naming convention.
do
-- Initialization code goes here ...
end
end </lang>
Add some Properties & Methods
Below, we've added three attributes (i.e. "Properties"). The "make" is not only a "Constructor" (Creation Procedure), but also an example of a "Method". <lang Eiffel> class MY_CLASS
create
make
feature {NONE} -- Initialization
make
-- This is a creation procedure or "Constructor".
do
create my_string.make_empty
end
feature -- Access (Properties)
my_string: STRING
-- This is a comment about `my_string', which is a "Property".
my_integer: INTEGER
-- Unlike `my_string' (above), the INTEGER type is an "Expanded Type".
-- This means INTEGER objects know how to self-initialize.
my_date: DATE
-- This attribute (or "Property") will need to be initialized.
-- One way to do that is to make a self-initializing attribute, thus ...
attribute
create Result.make_now
end
feature -- Basic Operations (Methods)
do_something
-- Loop over and print the numbers 1 to 100 to the console.
do
across 1 |..| 100 as i loop print (i.out) end
end
do_something_else
-- Set a and b and print the result.
local
a, b, c: INTEGER
do
a := 1
b := 2
c := a + b
end
end </lang>
Elena
ELENA 4.x : <lang elena>import extensions;
class MyClass {
prop int Variable;
someMethod()
{
Variable := 1
}
constructor()
{
}
}
public program() {
// instantiate the class
var instance := new MyClass();
// invoke the method
instance.someMethod();
// get the variable
console.printLine("Variable=",instance.Variable)
}</lang>
ERRE
ERRE isn't OOP-oriented, but with new PC version 3.0 is possibile to define classes and instance variables, like in this example: <lang ERRE>PROGRAM CLASS2_DEMO
CLASS QUADRATO
LOCAL LATO
PROCEDURE GETLATO(L)
LATO=L
END PROCEDURE
PROCEDURE AREA(->A)
A=LATO*LATO
END PROCEDURE
PROCEDURE PERIMETRO(->P)
P=4*LATO
END PROCEDURE
END CLASS
NEW P:QUADRATO,Q:QUADRATO
BEGIN
P_GETLATO(10) P_AREA(->AREAP) PRINT(AREAP) Q_GETLATO(20) Q_PERIMETRO(->PERIMETROQ) PRINT(PERIMETROQ)
END PROGRAM </lang> The answers is
100 80
F#
A minimal example as required by the task description: <lang fsharp>type MyClass(init) = // constructor with one argument: init
let mutable var = init // a private instance variable member x.Method() = // a simple method var <- var + 1 printfn "%d" var
// create an instance and use it let myObject = new MyClass(42) myObject.Method()</lang>
A somewhat more meaningful example, inspired by the Haskell version: <lang fsharp>open System
type Shape =
abstract Perimeter: unit -> float abstract Area: unit -> float
type Circle(radius) =
interface Shape with member x.Perimeter() = 2.0 * radius * Math.PI member x.Area() = Math.PI * radius**2.0
type Rectangle(width, height) =
interface Shape with member x.Perimeter() = 2.0 * width + 2.0 * height member x.Area() = width * height</lang>
Factor
<lang factor>TUPLE: my-class foo bar baz ; M: my-class quux foo>> 20 + ; C: <my-class> my-class 10 20 30 <my-class> quux ! result: 30 TUPLE: my-child-class < my-class quxx ; C: <my-child-class> my-child-class M: my-child-class foobar 20 >>quux ; 20 20 30 <my-child-class> foobar quux ! result: 30</lang>
Falcon
Falcon classes are a mix of data and code that can be used to instantiate objects. Classes are defined below. Note: inh1...inhN can also be passed the param_list. <lang falcon>class class_name[ ( param_list ) ] [ from inh1[, inh2, ..., inhN] ]
[ static block ] [ properties declaration ] [init block] [method list]
end</lang> Example of a class: <lang falcon>class mailbox( max_msg )
capacity = max_msg * 10
name = nil
messages = []
init
printl( "Box now ready for ", self.capacity, " messages." )
end
function slot_left()
return self.capacity - len( self.messages )
end
end</lang>
Instantiation: <lang falcon>m = mailbox( 10 ) // Ouputs: Box now ready for 100 messages.</lang>
Fancy
<lang fancy>class MyClass {
read_slot: 'instance_var # creates getter method for @instance_var @@class_var = []
def initialize {
# 'initialize' is the constructor method invoked during 'MyClass.new' by convention
@instance_var = 0
}
def some_method {
@instance_var = 1
@another_instance_var = "foo"
}
# define class methods: define a singleton method on the class object
def self class_method {
# ...
}
# you can also name the class object itself
def MyClass class_method {
# ...
}
}
myclass = MyClass new</lang>
Fantom
<lang Fantom>class MyClass {
// an instance variable
Int x
// a constructor, providing default value for instance variable
new make (Int x := 1)
{
this.x = x
}
// a method, return double the number x
public Int double ()
{
return 2 * x
}
}
class Main {
public static Void main ()
{
a := MyClass (2) // instantiates the class, with x = 2
b := MyClass() // instantiates the class, x defaults to 1
c := MyClass { x = 3 } // instantiates the class, sets x to 3
}
}</lang>
Forth
ANSI Forth has no object oriented features, but as Forth is a very easy language to extend, many object oriented programming systems have been implemented for it over the years. WinForth has one such system, which is described here.
Declare a class
<lang forth>:class MyClass <super Object
int memvar
:m ClassInit: ( -- )
ClassInit: super
1 to memvar ;m
:m ~: ( -- ) ." Final " show: [ Self ] ;m
:m set: ( n -- ) to memvar ;m :m show: ( -- ) ." Memvar = " memvar . ;m
- class</lang>
Allocate a static object <lang forth>MyClass newInstance</lang>
Allocate a dynamic object, saving its pointer in a global variable. <lang forth>New> MyClass value newInstance</lang>
Call member functions <lang forth>10 set: newInstance show: newInstance</lang>
Free a dynamically allocated object
<lang forth>newInstance dispose 0 to newInstance \ no dangling pointers!</lang>
Example of dynamic allocation and local variable use"
<lang forth>: test { \ obj -- }
New> MyClass to obj
show: obj
1000 set: obj
obj dispose ;</lang>
Works with any ANS Forth
Needs the FMS-SI (single inheritance) library code located here: http://soton.mpeforth.com/flag/fms/index.html <lang forth>include FMS-SI.f
- class foo \ begin class foo definition
ivar x \ declare an instance variable named x :m put ( n -- ) x ! ;m \ a method/message definition :m init: 10 self put ;m \ the constructor method :m print x ? ;m \ a print method for x
- class \ end class foo definition
foo f1 \ instantiate a foo object, in the dictionary, named f1 f1 print \ 10 send the print message to object f1 20 f1 put \ send a message with one parameter to the object f1 print \ 20
- bar \ bar is a normal Forth function definition
heap> foo \ instantiate a nameless object in the heap dup print 30 over put dup print <free ; \ destroy the heap object
- bar' \ bar' is an alternative to bar that uses a local variable
heap> foo {: f :}
f print
30 f put
f print
f <free ;
bar \ 10 30 bar' \ 10 30 </lang>
Fortran
Creating abstract derived type (abstract class), extended derived types, using constructor and finalization, pointers etc. Works with gfortran 5.0 and intel ifort 15.0.2
<lang fortran> !----------------------------------------------------------------------- !Module accuracy defines precision and some constants !----------------------------------------------------------------------- module accuracy_module
implicit none integer, parameter, public :: rdp = kind(1.d0) ! constants real(rdp), parameter :: pi=3.141592653589793238462643383279502884197_rdp
end module accuracy_module
!----------------------------------------------------------------------- !Module typedefs_module contains abstract derived type and extended type definitions. ! Note that a reserved word "class" in Fortran is used to describe ! some polymorphic variable whose data type may vary at run time. !----------------------------------------------------------------------- module typedefs_module
use accuracy_module implicit none
private ! all public :: TPoint, TShape, TCircle, TRectangle, TSquare ! public only these defined derived types
! abstract derived type
type, abstract :: TShape
real(rdp) :: area
character(len=:),allocatable :: name
contains
! deferred method i.e. abstract method = must be overridden in extended type
procedure(calculate_area), deferred,pass :: calculate_area
end type TShape
! just declaration of the abstract method/procedure for TShape type
abstract interface
function calculate_area(this)
use accuracy_module
import TShape !imports TShape type from host scoping unit and makes it accessible here
implicit none
class(TShape) :: this
real(rdp) :: calculate_area
end function calculate_area end interface
! auxiliary derived type
type TPoint
real(rdp) :: x,y
end type TPoint
! extended derived type
type, extends(TShape) :: TCircle
real(rdp) :: radius
real(rdp), private :: diameter
type(TPoint) :: centre
contains
procedure, pass :: calculate_area => calculate_circle_area
procedure, pass :: get_circle_diameter
final :: finalize_circle
end type TCircle
! extended derived type
type, extends(TShape) :: TRectangle
type(TPoint) :: A,B,C,D
contains
procedure, pass :: calculate_area => calculate_rectangle_area
final :: finalize_rectangle
end type TRectangle
! extended derived type
type, extends(TRectangle) :: TSquare
contains
procedure, pass :: calculate_area => calculate_square_area
final :: finalize_square
end type TSquare
contains
! finalization subroutines for each type
! They called recursively, i.e. finalize_rectangle
! will be called after finalize_square subroutine
subroutine finalize_circle(x)
type(TCircle), intent(inout) :: x
write(*,*) "Deleting TCircle object"
end subroutine finalize_circle
subroutine finalize_rectangle(x)
type(TRectangle), intent(inout) :: x
write(*,*) "Deleting also TRectangle object"
end subroutine finalize_rectangle
subroutine finalize_square(x)
type(TSquare), intent(inout) :: x
write(*,*) "Deleting TSquare object"
end subroutine finalize_square
function calculate_circle_area(this)
implicit none
class(TCircle) :: this
real(rdp) :: calculate_circle_area
this%area = pi * this%radius**2
calculate_circle_area = this%area
end function calculate_circle_area
function calculate_rectangle_area(this)
implicit none
class(TRectangle) :: this
real(rdp) :: calculate_rectangle_area
! here could be more code
this%area = 1
calculate_rectangle_area = this%area
end function calculate_rectangle_area
function calculate_square_area(this)
implicit none
class(TSquare) :: this
real(rdp) :: calculate_square_area
! here could be more code
this%area = 1
calculate_square_area = this%area
end function calculate_square_area
function get_circle_diameter(this)
implicit none
class(TCircle) :: this
real(rdp) :: get_circle_diameter
this % diameter = 2.0_rdp * this % radius
get_circle_diameter = this % diameter
end function get_circle_diameter
end module typedefs_module
!----------------------------------------------------------------------- !Main program !----------------------------------------------------------------------- program rosetta_class
use accuracy_module use typedefs_module implicit none
! we need this subroutine in order to show the finalization call test_types()
contains
subroutine test_types()
implicit none
! declare object of type TPoint
type(TPoint), target :: point
! declare object of type TCircle
type(TCircle),target :: circle
! declare object of type TSquare
type(TSquare),target :: square
! declare pointers
class(TPoint), pointer :: ppo
class(TCircle), pointer :: pci
class(TSquare), pointer :: psq
!constructor
point = TPoint(5.d0,5.d0)
ppo => point
write(*,*) "x=",point%x,"y=",point%y
pci => circle
pci % radius = 1
write(*,*) pci % radius
! write(*,*) pci % diameter !No,it is a PRIVATE component
write(*,*) pci % get_circle_diameter()
write(*,*) pci % calculate_area()
write(*,*) pci % area
psq => square
write(*,*) psq % area
write(*,*) psq % calculate_area()
write(*,*) psq % area
end subroutine test_types
end program rosetta_class
</lang>
FreeBASIC
<lang freebasic>' FB 1.05.0 Win64
Type MyClass
Private: myInt_ As Integer Public: Declare Constructor(myInt_ As Integer) Declare Property MyInt() As Integer Declare Function Treble() As Integer
End Type
Constructor MyClass(myInt_ As Integer)
This.myInt_ = myInt_
End Constructor
Property MyClass.MyInt() As Integer
Return myInt_
End Property
Function MyClass.Treble() As Integer
Return 3 * myInt_
End Function
Dim mc As MyClass = MyClass(24) Print mc.MyInt, mc.Treble() Print "Press any key to quit the program" Sleep</lang>
- Output:
24 72
GLSL
There are no classes in GLSL, but they can be simulated using structs: <lang glsl> struct Rectangle{
float width; float height;
};
Rectangle new(float width,float height){
Rectangle self; self.width = width; self.height = height; return self;
}
float area(Rectangle self){
return self.width*self.height;
}
float perimeter(Rectangle self){
return (self.width+self.height)*2.0;
} </lang>
Go
The task describes several concepts concerning class methods before giving some task requirements. The following code satisfies the task requirements. The concepts described however, are more involved. A discussion of these concepts follows. <lang go>package main
import "fmt"
// a basic "class." // In quotes because Go does not use that term or have that exact concept. // Go simply has types that can have methods. type picnicBasket struct {
nServings int // "instance variables" corkscrew bool
}
// a method (yes, Go uses the word method!) func (b *picnicBasket) happy() bool {
return b.nServings > 1 && b.corkscrew
}
// a "constructor." // Also in quotes as Go does not have that exact mechanism as part of the // language. A common idiom however, is a function with the name new<Type>, // that returns a new object of the type, fully initialized as needed and // ready to use. It makes sense to use this kind of constructor function when // non-trivial initialization is needed. In cases where the concise syntax // shown is sufficient however, it is not idiomatic to define the function. // Rather, code that needs a new object would simply contain &picnicBasket{... func newPicnicBasket(nPeople int) *picnicBasket {
// arbitrary code to interpret arguments, check resources, etc.
// ...
// return data new object.
// this is the concise syntax. there are other ways of doing it.
return &picnicBasket{nPeople, nPeople > 0}
}
// how to instantiate it. func main() {
var pb picnicBasket // create on stack (probably)
pbl := picnicBasket{} // equivalent to above
pbp := &picnicBasket{} // create on heap. pbp is pointer to object.
pbn := new(picnicBasket) // equivalent to above
forTwo := newPicnicBasket(2) // using constructor
// equivalent to above. field names, called keys, are optional.
forToo := &picnicBasket{nServings: 2, corkscrew: true}
fmt.Println(pb.nServings, pb.corkscrew) fmt.Println(pbl.nServings, pbl.corkscrew) fmt.Println(pbp) fmt.Println(pbn) fmt.Println(forTwo) fmt.Println(forToo)
}</lang>
- Output:
0 false
0 false
&{0 false}
&{0 false}
&{2 true}
&{2 true}
Transitive closure based on inheritance
Method polymorphism exists in Go with a type called interface. A Go interface is a method set. A type is said to satisfy an interface if it has defined on it all methods of the interface. If interface A is a subset of interface B then A satisfies B, so a transitive closure exists on this concept of satisfying an interface.
Inheritance is not involved however. A type satisfies an interface automatically when all methods of the interface are defined on the type. Inheritance is not involved because the interface being satisfied is not mentioned in any way, either in the type satisfying the interface or in its methods. The writer of a type and methods need not even be aware that the interface being satisfied exists.
Root type
The empty interface, with an empty method set and written as interface{}, is the “root type” in this context of transitive closure of interface satisfaction. All types satisfy the empty interface, since it makes no requirements that any methods be defined at all. interface{} is often used in go as a type that can hold a data value of any type. For example, note how fmt.Println, used above, accepts arguments of any type. It's (variadic) argument is of type interface{}.
Polymorphic dispatch
This happens when a method is called through an interface. Consider this code in addition to the example above. <lang go>import reflect
type happinessTester interface {
happy() bool
}
type bottleOfWine struct {
USD float64 empty bool
}
func (b *bottleOfWine) happy() bool {
return b.USD > 10 && !b.empty
}
func main() {
partySupplies := []happinessTester{
&picnicBasket{2, true},
&bottleOfWine{USD: 6},
}
for _, ps := range partySupplies {
fmt.Printf("%s: happy? %t\n",
reflect.Indirect(reflect.ValueOf(ps)).Type().Name(),
ps.happy())
}
}</lang> On the last line, in the call to ps.happy(), ps is of the interface type happinessTester. The method actually called is based on the underlying concrete type. For the method call, this is called the receiver type and the variable b (in both happy methods) is called the receiver. Dispatch is based on this single receiver so Go is a single dispatch kind of language.
Type tag
Go maintains something equivalent in its internal representation of interfaces. In place of direct access to internal data, Go's reflect package provides a number of functions for inspecting types and returning useful information. Shown above for example, is code recovering the name of the concrete type underlying the dynamic type of the interface.
- Output:
for second example
picnicBasket: happy? true bottleOfWine: happy? false
Distinction of types and classes
To the extent that an interface represents a class, it is distinct from a type that satisfies it. Interface is one kind of type, but an object of any type can satisfy an interface. The two types—the interface type and the type satisfying the interface—are distinct.
Groovy
A class: <lang groovy>/** Ye olde classe declaration */ class Stuff {
/** Heare bee anne instance variable declared */
def guts
/** This constructor converts bits into Stuff */
Stuff(injectedGuts) {
guts = injectedGuts
}
/** Brethren and sistren, let us flangulate with this fine flangulating method */
def flangulate() {
println "This stuff is flangulating its guts: ${guts}"
}
}</lang>
A demonstration: <lang groovy>def stuff = new Stuff( I have made mistakes in the past. I have made mistakes in the future.
-- Vice President Dan Quayle
)
stuff.flangulate()
stuff.guts = Our enemies are innovative and resourceful, and so are we. They never stop thinking about new ways to harm our country and our people, and neither do we.
-- President George W. Bush
stuff.flangulate()</lang>
- Output:
This stuff is flangulating its guts:
I have made mistakes in the past.
I have made mistakes in the future.
-- Vice President Dan Quayle
This stuff is flangulating its guts:
Our enemies are innovative and resourceful, and so are we.
They never stop thinking about new ways to harm our country and our people,
and neither do we.
-- President George W. Bush
Haskell
Haskell is entirely statically typed; that is, the type of every expression is completely determined at compile-time. Hence, the usual approach to object-oriented programming, in which the actual method invoked by a method call isn't determined until runtime (think of C++'s virtual functions), is impossible in Haskell 98. Haskell's type classes allow for polymorphic functions, but all the polymorphism happens at compile-time (think of C++ templates) without the use of language extensions (existential types). <lang haskell>class Shape a where
perimeter :: a -> Double area :: a -> Double
{- A type class Shape. Types belonging to Shape must support two methods, perimeter and area. -}
data Rectangle = Rectangle Double Double {- A new type with a single constructor. In the case of data types which have only one constructor, we conventionally give the constructor the same name as the type, though this isn't mandatory. -}
data Circle = Circle Double
instance Shape Rectangle where
perimeter (Rectangle width height) = 2 * width + 2 * height area (Rectangle width height) = width * height
{- We made Rectangle an instance of the Shape class by implementing perimeter, area :: Rectangle -> Int. -}
instance Shape Circle where
perimeter (Circle radius) = 2 * pi * radius area (Circle radius) = pi * radius^2
apRatio :: Shape a => a -> Double {- A simple polymorphic function. -} apRatio shape = area shape / perimeter shape
main = do
print $ apRatio $ Circle 5 print $ apRatio $ Rectangle 5 5
{- The correct version of apRatio (and hence the correct implementations of perimeter and area) is chosen based on the type of the argument. -}</lang>
The primary way to simulate run-time polymorphism in Haskell is to use a single algebraic data type with multiple constructors, rather than several types belonging to a single class.
<lang haskell>data Shape = Rectangle Double Double | Circle Double {- This Shape is a type rather than a type class. Rectangle and Circle are its constructors. -}
perimeter :: Shape -> Double {- An ordinary function, not a method. -} perimeter (Rectangle width height) = 2 * width + 2 * height perimeter (Circle radius) = 2 * pi * radius
area :: Shape -> Double area (Rectangle width height) = width * height area (Circle radius) = pi * radius^2
apRatio :: Shape -> Double {- Technically, this version of apRatio is monomorphic. -} apRatio shape = area shape / perimeter shape
main = do
print $ apRatio $ Circle 5 print $ apRatio $ Rectangle 5 5
{- The value returned by apRatio is determined by the return values of area and perimeter, which just happen to be defined differently for Rectangles and Circles. -}</lang>
Icon and Unicon
Unicon supports classes. <lang Unicon>class Example (x) # 'x' is a field in class
# method definition method double () return 2 * x end
# 'initially' block is called on instance construction
initially (x)
if /x # if x is null (not given), then set field to 0
then self.x := 0
else self.x := x
end
procedure main ()
x1 := Example () # new instance with default value of x x2 := Example (2) # new instance with given value of x write (x1.x) write (x2.x) write (x2.double ()) # call a method
end</lang>
J
Class definition: <lang j>coclass 'exampleClass'
exampleMethod=: monad define
1+exampleInstanceVariable
)
create=: monad define
'this is the constructor'
)
exampleInstanceVariable=: 0</lang>
Instantiation: <lang j> exampleObject=: conew 'exampleClass'</lang>
Note that all J system defined utilities designed specifically to work on classes and objects have names which begin with the prefix co.
Java
<lang java>public class MyClass{
// instance variable private int variable; // Note: instance variables are usually "private"
/**
* The constructor
*/
public MyClass(){
// creates a new instance
}
/**
* A method
*/
public void someMethod(){
this.variable = 1;
}
}</lang> Note: "this." in someMethod is optional. "variable = 1;" works also. If a parameter also named "variable" came into someMethod, using "this" specifies using the instance variable rather than the local method variable. Instantiate this class using: <lang java>new MyClass();</lang>
JavaScript
ES5
JavaScript is prototype-based, so it doesn't have classes per se. Thinking in classes when coding JavaScript will only hinder you in the long run, but here's an example of JavaScript OO:
<lang javascript>//Constructor function. function Car(brand, weight) {
this.brand = brand; this.weight = weight || 1000; // Resort to default value (with 'or' notation).
} Car.prototype.getPrice = function() { // Method of Car.
return this.price;
}
function Truck(brand, size) {
this.car = Car; this.car(brand, 2000); // Call another function, modifying the "this" object (e.g. "superconstructor".) this.size = size; // Custom property for just this object.
} Truck.prototype = Car.prototype; // Also "import" the prototype from Car.
var cars = [ // Some example car objects.
new Car("Mazda"),
new Truck("Volvo", 2)
]; for (var i=0; i<cars.length; i++) {
alert(cars[i].brand + " " + cars[i].weight + " " + cars[i].size + ", " +
(cars[i] instanceof Car) + " " + (cars[i] instanceof Truck));
}</lang> The alerts shows us:
Mazda 1000 undefined, true true Volvo 2000 2, true true
The reason Car shows as instanceof Truck is because we've overwritten Truck.prototype with Car.prototype. It's probably not the best way to do it, but it suffices for most cases.
ES6
<lang javascript>class Car {
/**
* A few brands of cars
* @type {string[]}
*/
static brands = ['Mazda', 'Volvo'];
/**
* Weight of car
* @type {number}
*/
weight = 1000;
/**
* Brand of car
* @type {string}
*/
brand;
/**
* Price of car
* @type {number}
*/
price;
/**
* @param {string} brand - car brand
* @param {number} weight - mass of car
*/
constructor(brand, weight) {
if (brand) this.brand = brand;
if (weight) this.weight = weight
}
/**
* Drive
* @param distance - distance to drive
*/
drive(distance = 10) {
console.log(`A ${this.brand} ${this.constructor.name} drove ${distance}cm`);
}
/**
* Formatted stats string
*/
get formattedStats() {
let out =
`Type: ${this.constructor.name.toLowerCase()}`
+ `\nBrand: ${this.brand}`
+ `\nWeight: ${this.weight}`;
if (this.size) out += `\nSize: ${this.size}`;
return out }
}
class Truck extends Car {
/**
* Size of truck
* @type {number}
*/
size;
/**
* @param {string} brand - car brand
* @param {number} size - size of car
*/
constructor(brand, size) {
super(brand, 2000);
if (size) this.size = size;
}
}
let myTruck = new Truck('Volvo', 2); console.log(myTruck.formattedStats); myTruck.drive(40);</lang>
Output:
Type: truck Brand: Volvo Weight: 2000 Size: 2 A Volvo Truck drove 40cm
Julia
Julia has inheritable types and abstract classes but does not have multiple inheritance. Multiple dispatch is a core feature of the language.
<lang julia>abstract type Mammal end habitat(::Mammal) = "planet Earth"
struct Whale <: Mammal
mass::Float64 habitat::String
end Base.show(io::IO, ::Whale) = print(io, "a whale") habitat(w::Whale) = w.habitat
struct Wolf <: Mammal
mass::Float64
end Base.show(io::IO, ::Wolf) = print(io, "a wolf")
arr = [Whale(1000, "ocean"), Wolf(50)] println("Type of $arr is ", typeof(arr)) for a in arr
println("Habitat of $a: ", habitat(a))
end</lang>
- Output:
Type of Mammal[a whale, a wolf] is Array{Mammal,1}
Habitat of a whale: ocean
Habitat of a wolf: planet Earth
Kotlin
<lang scala>class MyClass(val myInt: Int) {
fun treble(): Int = myInt * 3
}
fun main(args: Array<String>) {
val mc = MyClass(24)
print("${mc.myInt}, ${mc.treble()}")
}</lang>
- Output:
24, 72
Lasso
In Lasso, a "class" is termed a "type"
<lang Lasso> define mytype => type { data public id::integer = 0, public val::string = , public rand::integer = 0
public onCreate() => { // "onCreate" runs when instance created, populates .rand .rand = math_random(50,1) } public asString() => { return 'has a value of: "'+.val+'" and a rand number of "'+.rand+'"' }
}
local(x = mytype)
- x->val = '99 Bottles of beer'
- x->asString // outputs 'has a value of: "99 Bottles of beer" and a rand number of "48"'</lang>
LFE
<lang lisp> (defmodule simple-object
(export all))
(defun fish-class (species)
"
This is the constructor used internally, once the children and fish id are
known.
"
(let ((habitat '"water"))
(lambda (method-name)
(case method-name
('habitat
(lambda (self) habitat))
('species
(lambda (self) species))))))
(defun get-method (object method-name)
" This is a generic function, used to call into the given object (class instance). " (funcall object method-name))
- define object methods
(defun get-habitat (object)
"Get a variable set in the class." (funcall (get-method object 'habitat) object))
(defun get-species (object)
"Get a variable passed when constructing the object." (funcall (get-method object 'species) object))
</lang>
Usage from the LFE REPL: <lang lisp> > (slurp '"simple-object.lfe")
- (ok simple-object)
> (set my-fish (fish-class '"Carp"))
- Fun<lfe_eval.10.91765564>
> (get-habitat my-fish) "water" > (get-species my-fish) "Carp" </lang>
Lingo
Class definition: <lang lingo>---------------------------------------- -- @desc Class "MyClass" -- @file parent script "MyClass"
-- instance variable property _myvar
-- constructor on new (me)
me._myvar = 23 return me
end
-- a method on doubleAndPrint (me)
me._myvar = me._myvar * 2 put me._myvar
end</lang>
Instantiation: <lang lingo>foo = script("MyClass").new() foo.doubleAndPrint() -- 46</lang>
Lisaac
<lang Lisaac>Section Header
+ name := SAMPLE;
Section Inherit
- parent : OBJECT := OBJECT;
Section Private
+ variable : INTEGER <- 0;
Section Public
- some_method <- (
variable := 1;
);
- main <- (
+ sample : SAMPLE;
sample := SAMPLE.clone; sample.some_method;
);</lang>
Logtalk
The definition of classes in Logtalk require the use of meta-classes. In order to avoid infinite regression, we use here the usual trick of making a class an instance of itself. The class meta-class holds the constructor method, allowing the class to accept a message for creating a new instance. The class itself defines the methods and variables of its instances. <lang logtalk>:- object(metaclass,
instantiates(metaclass)).
:- public(new/2).
new(Instance, Value) :-
self(Class),
create_object(Instance, [instantiates(Class)], [], [state(Value)]).
- - end_object.
- - object(class,
instantiates(metaclass)).
:- public(method/1).
method(Value) :-
::state(Value).
:- private(state/1).
- - end_object.</lang>
A simple usage example after compiling and loading the above code: <lang logtalk>| ?- class::new(Instance, 1). Instance = o1 yes
| ?- o1::method(Value). Value = 1 yes</lang>
Lua
Classes in Lua are implemented with metatables. This doesn't implement a full system, but it gets the basic idea: <lang lua>myclass = setmetatable({ __index = function(z,i) return myclass[i] end, --this makes class variables a possibility setvar = function(z, n) z.var = n end }, { __call = function(z,n) return setmetatable({var = n}, myclass) end })
instance = myclass(3)
print(instance.var) -->3
instance:setvar(6)
print(instance.var) -->6</lang>
M2000 Interpreter
<lang M2000 Interpreter> Class zz {
module bb {
Superclass A {
unique:
counter
}
Superclass B1 {
unique:
counter
}
Superclass B2 {
unique:
counter
}
\\ We can make a group Alfa with a member, another group Beta
\\ Group Beta can't see parent group, but can see own member groups
\\ Group Alfa can see everything in nested groups, in any level,
\\ but can't see inside modules/functions/operator/value/set
Group Alfa {
Group Beta { }
}
Alfa=A
Alfa.Beta=B1
\\ we make 3 groups for marshaling counters
\\ each group get a superclass
Marshal1=A
Marshal2=B1
Marshal3=B2
\\ Now we want to add functionality7
\\ Inc module to add 1 to counter
\\ a Value function to return counter
\\ Without Value a group return a copy
\\ If a group has a value then we can get copy using Group(nameofgroup)
\\ just delete Group Marshal1 and remove Rem when we make Marshal1 using a class function
Group Marshal1 {
Module Inc {
For SuperClass {.counter++}
}
Value {
For SuperClass {=.counter}
}
}
Class AnyMarshal {
Module Inc {
For SuperClass {.counter++}
}
Value {
For SuperClass {=.counter}
}
}
\\ here we merge groups
Rem : Marshal1=AnyMarshal()
Marshal2=AnyMarshal()
Marshal3=AnyMarshal()
\\ So now we see counters (three zero)
Print Marshal1, Marshal2, Marshal3 \\ 0, 0, 0
\\ Now we prepare Alfa and Alfa.Beta groups
Group Alfa {
Group Beta {
Function SuperClass.Counter {
For SuperClass {
=.counter
}
}
}
Module PrintData {
For SuperClass {
Print .counter, This.Beta.SuperClass.Counter()
}
}
}
\\ some marshaling to counters
Marshal1.inc
Marshal2.inc
Marshal2.inc
Marshal3.inc
\\ lets print results
Print Marshal1, Marshal2, Marshal3 \\ 1 2 1
\\ Calling Alfa.PrintData
Alfa.PrintData \\ 1 2
\\ Merging a group in a group make a change to superclass pointer inside group
Alfa.Beta=B2 \\ change supeclass
Alfa.PrintData \\ 1 1
For i=1 to 10 : Marshal3.inc : Next i
Alfa.PrintData \\ 1 11
Alfa.Beta=B1 \\ change supeclass
Alfa.PrintData \\ 1 2
Epsilon=Alfa
Print Valid(@alfa as epsilon), Valid(@alfa.beta as epsilon.beta) \\ -1 -1
Epsilon.PrintData \\ 1 2
Alfa.Beta=B2 \\ change supeclass
Alfa.PrintData \\ 1 11
Epsilon.PrintData \\ 1 2
\\ validation being for top group superclass and all members if are same
\\ but not for inner superclasses. This maybe change in later revisions of language.
Print Valid(@alfa as epsilon), Valid(@alfa.beta as epsilon.beta) \\ -1 0
}
} Dim A(10) A(3)=zz() A(3).bb
Report { there is no super like java super in M2000 when we use inheritance through classes see Superclass (example SUP) which is something differnent }
class Shape {
private:
super.X, super.Y
Function super.toString$(a=10) {
="Shape(" + str$(.super.X,"") + ", " + str$(.super.Y,"") + ")"
}
public:
Module final setPosition (px, py) {
.super.X <= px
.super.Y <= py
}
Function toString$() {
=.super.toString$()
}
} class MoveShape {
Module MoveRelative(xr, yr) {
.super.X+=xr
.super.Y+=yr
}
} class Circle as MoveShape as Shape { private:
radius
public:
Module setRadius (r) {
.radius <= r
}
Function toString$() {
= .super.toString$() + ": Circle(" + str$(.radius,"") + ")"
}
}
class Rectangle as MoveShape as Shape { private:
height, width
public:
Module MoveLeftSide (p as *Rectangle) {
\\ for same type objects private members are like public
for This, p {
.super.X<=..super.X+..width
.super.Y<=..super.Y
}
}
module setDimensions (h,w) {
.height <= h
.width <= w
}
Function toString$() {
= .super.toString$() + ": Rectangle(" + str$(.height,"") + " x " + str$(.width,"") + ")"
}
} c =Circle() r = Rectangle()
r.setPosition 1, 2 r.setDimensions 50, 50 c.setPosition 3, 4 c.setRadius 10 Print r.tostring$() Print c.tostring$() r.MoveRelative 100,100 c.MoveRelative -50,-50 Print r.tostring$() Print c.tostring$()
Report { wokring with pointers like in c++ pointers in M2000 are objects, so null pointer (pc->0&) isn't a zero, but an empty Group (object) } pc->circle() pr->rectangle() pr=>setPosition 1, 2 pr=>setDimensions 50, 50 pc=>setPosition 3, 4 pc=>setRadius 10 Print pr=>tostring$() Print pc=>tostring$() \\ we can open up to ten objects (from one to ten dots, normaly one to three) \\ if we use nestef for object {} also we have up to ten objects in total \\ every for object {} is an area for temporary definitions, after exit from brackets \\ any new definition erased. For pr, pc { .MoveRelative 100,100 ..MoveRelative -50,-50 Print .tostring$() Print ..tostring$() } pr2->rectangle() pr2=>SetDimensions 30, 30 pr2=>MoveLeftSide pr Print pr2=>toString$()
</lang>
MATLAB
There are two ways to declare classes in MATLAB: with a classdef or without it. First you must create a folder named after the class type that you are defining with an "@" appended to the front, e.g. "@LinkedList", in your MATLAB root directory. In this folder you put all of the class methods and, if you have it, the classdef. Any MATLAB buitlin methods can be overloaded for any class you define. For example, if you want to overload the "+" operator, create an .m file in the class folder named "plus.m". Furthermore, all class variables have to be generated in the class constructor if a classdef is not going to be used.
Below are two examples of classes declared in MATLAB. GenericClass is defined without a classdef. GenericClass2 is defined with a classdef. The classes both do the exact same thing, the only difference between them is how they are defined.
@GenericClass
GenericClass.m: Class Constructor <lang MATLAB>function GenericClassInstance = GenericClass(varargin)
if isempty(varargin) %No input arguments
GenericClassInstance.classVariable = 0; %Generates a struct
else
GenericClassInstance.classVariable = varargin{1}; %Generates a struct
end
%Converts the struct to a class of type GenericClass
GenericClassInstance = class(GenericClassInstance,'GenericClass');
end</lang> getValue.m: <lang MATLAB>%Get function function value = getValue(GenericClassInstance)
value = GenericClassInstance.classVariable;
end</lang> setValue.m: <lang MATLAB>%Set function function GenericClassInstance = setValue(GenericClassInstance,newValue)
GenericClassInstance.classVariable = newValue;
end</lang> display.m: This method overloads the "disp()" command <lang MATLAB>function display(GenericClassInstance)
disp(sprintf('%f',GenericClassInstance.classVariable));
end</lang>
Sample Usage: <lang MATLAB>>> myClass = GenericClass(3) 3.000000 >> myClass = setValue(myClass,pi) 3.141593 >> getValue(myClass)
ans =
3.141592653589793</lang>
@GenericClass2 GenericClass2.m: This is the classdef, it includes the class constructor as well as class variables and methods. <lang MATLAB>classdef GenericClass2
properties
classVariable
end %properties
methods
%Class constructor
function objectInstance = GenericClass2(varargin)
if isempty(varargin) %No input arguments
objectInstance.classVariable = 0;
else
objectInstance.classVariable = varargin{1};
end
end
%Set function
function setValue(GenericClassInstance,newValue)
GenericClassInstance.classVariable = newValue;
%MATLAB magic that changes the object in the scope that called
%this set function.
assignin('caller',inputname(1),GenericClassInstance);
end
end %methods
end</lang> getValue.m: <lang MATLAB>%Get function function value = getValue(GenericClassInstance)
value = GenericClassInstance.classVariable;
end</lang> display.m: This method overloads the "disp()" command <lang MATLAB>function display(GenericClassInstance)
disp(sprintf('%f',GenericClassInstance.classVariable));
end</lang>
Sample Usage: <lang MATLAB>>> myClass = GenericClass2(3) 3.000000 >> setValue(myClass,pi) >> getValue(myClass)
ans =
3.141592653589793</lang>
MiniScript
<lang MiniScript>// MiniScript is prototype based Weapon = { "name": "Sword", "damage": 3 } Weapon.slice = function()
print "Did " + self.damage + " damage with " + self.name
end function
wep = new Weapon // Same as: wep = { "__isa": Weapon }
wep.name = "Lance"
wep.slice</lang>
Nanoquery
<lang nanoquery>class MyClass declare name
// constructors are methods with the same name as the class def MyClass(name) this.name = name end
def getName() return name end end
// instantiate a new MyClass object inst = new(MyClass, "name string goes here")
// display the name value println inst.getName()</lang>
Nemerle
<lang Nemerle>public class MyClass {
public this() { } // the constructor in Nemerle is always named 'this'
public MyVariable : int
{
get;
set;
}
public MyMethod() : void
{
}
}
def myInstance = MyClass(); // no 'new' keyword needed myInstance.MyVariable = 42; // set MyVariable System.Console.WriteLine($"My variable is $(myInstance.MyVariable)") // get MyVariable</lang>
NetRexx
<lang rexx>class ClassExample
properties private -- class scope foo = int properties public -- publicly visible bar = boolean properties indirect -- generates bean patterns baz = String() method main(args=String[]) static -- main method clsex = ClassExample() -- instantiate clsex.foo = 42 clsex.baz = 'forty-two' clsex.bar = 0 -- boolean false clsex.test(clsex.foo) clsex.test(clsex.bar) clsex.test(clsex.baz)
method test(s=int) aap = 1 -- local (stack) variable say s aap
method test(s=String) noot = 2 say s noot
method test(s=boolean) mies = 3 say s mies</lang>
Nim
<lang nim>type MyClass = object
name: int
proc initMyClass(): MyClass =
result.name = 2
proc someMethod(m: var MyClass) =
m.name = 1
var mc = initMyClass() mc.someMethod()
type
Gender = enum male, female, other
MyOtherClass = object name: string gender: Gender age: Natural
proc initMyOtherClass(name; gender = female; age = 50): auto =
MyOtherClass(name: name, gender: gender, age: age)
var person1 = initMyOtherClass("Jane") echo person1.name, " ", person1.gender, " ", person1.age # Jane female 50 var person2 = initMyOtherClass("John", male, 23) echo person2.name, " ", person2.gender, " ", person2.age # John male 23</lang>
Oberon-2
<lang oberon2>MODULE M;
TYPE
T = POINTER TO TDesc;
TDesc = RECORD
x: INTEGER
END;
PROCEDURE New*(): T;
VAR t: T;
BEGIN
NEW(t); t.x := 0;
RETURN t
END New;
PROCEDURE (t: T) Increment*;
BEGIN
INC(t.x)
END Increment;
END M.</lang>
Exported procedures are marked with an asterisk (*). There is nothing special about the constructor New, it is just a function that returns a new object of type T. The name of the method receiver can also be chosen freely. INC is a predeclared procedure that increments its argument.
Objeck
<lang objeck>bundle Default {
class MyClass {
@var : Int;
New() {
}
method : public : SomeMethod() ~ Nil {
@var := 1;
}
method : public : SetVar(var : Int) ~ Nil {
@var := var;
}
method : public : GetVar() ~ Int {
return @var;
}
}
class Test {
function : Main(args : String[]) ~ Nil {
inst := MyClass->New();
inst->GetVar()->PrintLine();
inst->SomeMethod();
inst->GetVar()->PrintLine();
inst->SetVar(15);
inst->GetVar()->PrintLine();
}
}
}</lang>
Object Pascal
- Note: This is not part of standard Pascal, but Turbo Pascal specific
<lang pascal>type
MyClass = object
variable: integer;
constructor init;
destructor done;
procedure someMethod;
end;
constructor MyClass.init;
begin variable := 0; end;
procedure MyClass.someMethod;
begin variable := 1; end;
var
instance: MyClass; { as variable }
pInstance: ^MyClass; { on free store }
begin
{ create instances }
instance.init;
new(pInstance, init); { alternatively: pInstance := new(MyClass, init); }
{ call method }
instance.someMethod;
pInstance^.someMethod;
{ get rid of the objects }
instance.done;
dispose(pInstance, done);
end;</lang>
Objective-C
Interface: <lang objc>// There are no class variables, so static variables are used. static int myClassVariable = 0;
@interface MyClass : NSObject {
int variable; // instance variable
}
- (int)variable; // Typical accessor - you should use the same name as the variable
@end</lang>
Implementation:
<lang objc>@implementation MyClass
// Was not declared because init is defined in NSObject - (instancetype)init {
if (self = [super init]) {
variable = 0; // not strictly necessary as all instance variables are initialized to zero
}
return self;
}
- (int)variable {
return variable;
}
@end</lang>
Using the class:
<lang objc>// Creating an instance MyClass *mc = [[MyClass alloc] init];
// Sending a message [mc variable];</lang>
OCaml
<lang ocaml>class my_class =
object (self) val mutable variable = 0 method some_method = variable <- 1 end</lang>
Using the class:
# let instance = new my_class;; val instance : my_class = <obj> # instance#some_method;; - : unit = ()
Oforth
Class creation <lang Oforth>Object Class new: MyClass(att) MyClass method: initialize(v) v := att ;</lang>
Usage : instantiation <lang Oforth>MyClass new("some value")</lang>
Ol
Otus Lisp have no classes support.
ooRexx
ooRexx classes are defined using directives. Only methods of the class can directly access instance variables to avoid fragile base class problems, methods can only access variables at the level of the class hierarchy they are defined. ::attribute directives create setter and getter methods that allow instance variables to be accessed in other contexts.
<lang ooRexx>p = .point~new c = .circle~new
p~print c~print
- class point
- method init
expose x y use strict arg x = 0, y = 0 -- defaults to 0 for any non-specified coordinates
- attribute x
- attribute y
- method print
expose x y
say "A point at location ("||x","y")"
- class circle subclass point
- method init
expose radius use strict arg x = 0, y = 0, radius = 0 self~init:super(x, y) -- call superclass constructor
- attribute radius
- method print
expose radius
say "A circle of radius" radius "centered at location ("||self~x","self~y")"</lang>
OxygenBasic
Example of a dynamic object. (statically defined objects do not require specific constructors and destructors.)
Parameter polymorphism is supported both by method overloading and also by automatic type conversion between integers, floats, strings and other primitives.
<lang oxygenbasic>
class SuperString
indexbase 1
union
bstring s sys bs sys *y int *i byte *b float *f
end union
method space(sys n)
s=space n
end method
method delete()
freememory bs : bs=0
end method
method clear()
sys j, le=length if le then for j=1 to le : b[j]=0 : next end if
end method
method length() as sys
if bs then return i[0]
end method
method resize(sys n)
sys le=length if n<le s=left s,n elseif n>le s+=nuls n-le end if
end method
method fill(string f)
sys j, ls=length, lf=len f for j=1 to ls step lf mid s,j,f next
end method
method constructor() end method
method destructor
delete
end method
end class
'#recordof SuperString
'===== 'TESTS '=====
new SuperString ss ' ss.space 100 ss.resize 8 ss.fill "abc" ' print ss.s 'result abcabcab print ss.b[3] 'result 99: ascii for 'c' ' del ss </lang>
Oz
Classes are created at runtime and first-class values. <lang oz>declare
class Something
feat
name %% immutable, public attribute (called a "feature")
attr
count %% mutable, private attribute
%% public method which is used as an initializer
meth init(N)
self.name = N
count := 0
end
%% public method
meth increase
count := @count + 1
end
end
in
%% create an instance
Object = {New Something init("object")}
%% call a method
{Object increase}</lang>
Pascal
See Delphi
Perl
The implementation (there are no declarations) of a class using the standard object system: <lang perl>{
# a class is a package (i.e. a namespace) with methods in it package MyClass;
# a constructor is a function that returns a blessed reference
sub new {
my $class = shift;
bless {variable => 0}, $class;
# the instance object is a hashref in disguise.
# (it can be a ref to anything.)
}
# an instance method is a function that takes an object as first argument.
# the -> invocation syntax takes care of that nicely, see Usage paragraph below.
sub some_method {
my $self = shift;
$self->{variable} = 1;
}
}</lang>
This is the same using the Moose object system: <lang perl>{
package MyClass; use Moose;
has 'variable' => (is => 'rw', default => 0); # constructor and accessor methods are added automatically
sub some_method {
my $self = shift;
$self->variable(1);
}
}</lang>
This is the same class using the MooseX::Declare extention: <lang perl>use MooseX::Declare; class MyClass {
has 'variable' => (is => 'rw', default => 0);
method some_method {
$self->variable(1);
}
}</lang>
All of the above classes can be used the same way: <lang perl>my $instance = MyClass->new; # invoke constructor method
$instance->some_method; # invoke method on object instance
# instance deallocates when the last reference falls out of scope</lang>
Phix
Note that constructors/destructors are not yet finalised (hopefully 0.8.2). Needs 0.8.1+ <lang Phix>class Number
public integer n = 3
procedure show()
printf(1,"show: n is %d\n",{n})
end procedure
end class Number v = new({4}) ?v.n v.n = 5 v.show()</lang>
- Output:
4 show: n is 5
PHL
<lang phl>module classes;
extern printf;
class @MyClass { field @Integer myField { get:get_myField, set:set_myField };
new [ this.set_myField(2); ]
@Void method [ this.set_myField(this::get_myField + 1); ] };
@Integer main [ var obj = new @MyClass; printf("obj.myField: %i\n", obj::get_myField); obj::method; printf("obj.myField: %i\n", obj::get_myField); return 0; ]</lang>
PHP
<lang php>class MyClass {
public static $classVar;
public $instanceVar; // can also initialize it here
function __construct() {
$this->instanceVar = 0;
}
function someMethod() {
$this->instanceVar = 1;
self::$classVar = 3;
}
} $myObj = new MyClass();</lang>
PicoLisp
<lang PicoLisp>(class +Rectangle)
- dx dy
(dm area> () # Define a a method that calculates the rectangle's area
(* (: dx) (: dy)) )
(println # Create a rectangle, and print its area
(area> (new '(+Rectangle) 'dx 3 'dy 4)) )</lang>
Pop11
Object system is implemented as a library, so we must first load it. <lang pop11>uses objectclass; define :class MyClass;
slot value = 1;
enddefine;</lang>
Defining class MyClass automatically defines two constructors, newMyClass and consMyClass and slot (instance variable) accessors, so we can immediately start using our new class:
<lang pop11>;;; Construct instance with default slot values lvars instance1 = newMyClass();
- Construct instance with explicitely given slot values
lvars instance2 = consMyClass(15);
- Print slot value using dot notation
instance1.value => instance2.value =>
- Print slot value using funtional notation
value(instance1) =>
- Change slot value
12 -> value(instance1);
- Print it
value(instance1) =></lang>
We can add methods at any time (even after creating an instance):
<lang pop11>define :method reset(x : MyClass);
0 -> value(x);
enddefine; reset(instance1);
- Print it
instance1 =></lang>
PowerShell
Prior to PowerShell 5, native class definition was not supported in PowerShell. But you could define classes in PowerShell using C#, JavaScript, or VisualBasic. <lang powershell> Add-Type -Language CSharp -TypeDefinition @' public class MyClass {
public MyClass()
{
}
public void SomeMethod()
{
}
private int _variable;
public int Variable
{
get { return _variable; }
set { _variable = value; }
}
public static void Main()
{
// instantiate it
MyClass instance = new MyClass();
// invoke the method
instance.SomeMethod();
// set the variable
instance.Variable = 99;
// get the variable
System.Console.WriteLine( "Variable=" + instance.Variable.ToString() );
}
} '@ </lang>
Basic syntax
<lang PowerShell>
class MyClass
{
[type]$MyProperty1
[type]$MyProperty2 = "Default value"
# Constructor
MyClass( [type]$MyParameter1, [type]$MyParameter2 )
{
# Code
}
# Method ( [returntype] defaults to [void] )
[returntype] MyMethod( [type]$MyParameter3, [type]$MyParameter4 )
{
# Code
}
} </lang> Example class <lang PowerShell> class Banana {
- Properties
[string]$Color [boolean]$Peeled
- Default constructor
Banana()
{
$This.Color = "Green"
}
- Constructor
Banana( [boolean]$Peeled )
{
$This.Color = "Green"
$This.Peeled = $Peeled
}
- Method
Ripen()
{
If ( $This.Color -eq "Green" ) { $This.Color = "Yellow" }
Else { $This.Color = "Brown" }
}
- Method
[boolean] IsReadyToEat()
{
If ( $This.Color -eq "Yellow" -and $This.Peeled ) { return $True }
Else { return $False }
}
} </lang> Using the example class <lang PowerShell> $MyBanana = [banana]::New() $YourBanana = [banana]::New( $True ) $YourBanana.Ripen() If ( -not $MyBanana.IsReadyToEat() -and $YourBanana.IsReadyToEat() )
{ $MySecondBanana = $YourBanana }
</lang>
Processing
<lang java>class ProgrammingLanguage {
// instance variable:
private String name;
// constructor (let's use it to give the instance variable a value):
public ProgrammingLanguage(String name)
{
this.name = name;
// note use of "this" to distinguish the instance variable from the argument
}
// a method:
public void sayHello()
{
println("Hello from the programming language " + name);
// the method has no argument or local variable called "name", so we can omit the "this"
}
}</lang> How to use it: <lang java>// instantiate the class: ProgrammingLanguage processing = new ProgrammingLanguage("Processing");
// call the method: processing.sayHello();</lang>
- Output:
Hello from the programming language Processing
PureBasic
Generic version
<lang PureBasic>Interface OO_Interface ; Interface for any value of this type
Get.i() Set(Value.i) ToString.s() Destroy()
EndInterface
Structure OO_Structure ; The *VTable structure
Get.i Set.i ToString.i Destroy.i
EndStructure
Structure OO_Var
*VirtualTable.OO_Structure Value.i
EndStructure
Procedure OO_Get(*Self.OO_Var)
ProcedureReturn *Self\Value
EndProcedure
Procedure OO_Set(*Self.OO_Var, n)
*Self\Value = n
EndProcedure
Procedure.s OO_ToString(*Self.OO_Var)
ProcedureReturn Str(*Self\Value)
EndProcedure
Procedure Create_OO()
*p.OO_Var=AllocateMemory(SizeOf(OO_Var)) If *p *p\VirtualTable=?VTable EndIf ProcedureReturn *p
EndProcedure
Procedure OO_Destroy(*Self.OO_Var)
FreeMemory(*Self)
EndProcedure
DataSection
VTable: Data.i @OO_Get() Data.i @OO_Set() Data.i @OO_ToString() Data.i @OO_Destroy()
EndDataSection
- - Test the code
- Foo.OO_Interface = Create_OO()
- Foo\Set(341)
MessageRequester("Info", "Foo = " + *Foo\ToString() )
- Foo\Destroy()</lang>
Simple OOP Version
Using the open-source precompiler SimpleOOP. <lang PureBasic>Class Foo
Private Value.i
BeginPublic
Method Init()
; Any needed code goes here
EndMethod
Method Release()
; Any code befoe freeing the object goes here
EndMethod
Method Get()
MethodReturn This\Value
EndMethod
Method Set(n)
This\Value = n
EndMethod
Method.s ToString()
MethodReturn Str(This\Value)
EndMethod
EndPublic
EndClass
- - Test the code
- Demo.foo = NewObject.foo()
- Demo\Set(4)
MessageRequester("Info", "Val= " + *Demo\ToString())</lang>
Python
<lang python>class MyClass:
name2 = 2 # Class attribute
def __init__(self):
"""
Constructor (Technically an initializer rather than a true "constructor")
"""
self.name1 = 0 # Instance attribute
def someMethod(self):
"""
Method
"""
self.name1 = 1
MyClass.name2 = 3
myclass = MyClass() # class name, invoked as a function is the constructor syntax.
class MyOtherClass:
count = 0 # Population of "MyOtherClass" objects
def __init__(self, name, gender="Male", age=None):
"""
One initializer required, others are optional (with different defaults)
"""
MyOtherClass.count += 1
self.name = name
self.gender = gender
if age is not None:
self.age = age
def __del__(self):
MyOtherClass.count -= 1
person1 = MyOtherClass("John") print person1.name, person1.gender # "John Male" print person1.age # Raises AttributeError exception! person2 = MyOtherClass("Jane", "Female", 23) print person2.name, person2.gender, person2.age # "Jane Female 23"</lang>
Python allows for very flexible argument passing including normal named parameters, defaulted/optional named parameters, up to one "varargs" tuple, and any number of keywords arguments (which are all passed in the form of a single dictionary (associative array), and any non-ambiguous combination of these). All types of argument passing for functions can also be used for object instantiation/initialization (passed to the special __init__() method) as shown.
New-style classes inherit from "object" or any descendant of the "object" class:
<lang python>class MyClass(object):
...</lang>
These "new-style" classes support some features which were unavailable in "classic classes". New features include a __new__() with lower level control over object instantiation, metaclass support, static methods, class methods, "properties" (managed attributes) and "slots" (attribute restrictions).
R
R has (at least) 5 different object oriented systems. S3 and S4 correspond to different versions of the S language, from which R was derived. See, for example, this presentation by Freidrich Leisch for a more thorough introduction to S3 and S4 classes. Both these class systems are in use, and ship with the standard R distribution. The OOP, R.oo and proto packages provide other systems.
S3
S3 provides a very simple class system designed to be easily used interactively. <lang R>#You define a class simply by setting the class attribute of an object circS3 <- list(radius=5.5, centre=c(3, 4.2)) class(circS3) <- "circle"
- plot is a generic function, so we can define a class specific method by naming it plot.classname
plot.circle <- function(x, ...) {
t <- seq(0, 2*pi, length.out=200)
plot(x$centre[1] + x$radius*cos(t),
x$centre[2] + x$radius*sin(t),
type="l", ...)
} plot(circS3)</lang>
S4
S4 is a more formal class system that provides validity checking and a way to define different methods for different input signatures. <lang R>setClass("circle",
representation(
radius="numeric",
centre="numeric"),
prototype(
radius=1,
centre=c(0,0)))
- Instantiate class with some arguments
circS4 <- new("circle", radius=5.5)
- Set other data slots (properties)
circS4@centre <- c(3,4.2)
- Define a method
setMethod("plot", #signature("circle"),
signature(x="circle", y="missing"),
function(x, ...)
{
t <- seq(0, 2*pi, length.out=200)
#Note the use of @ instead of $
plot(x@centre[1] + x@radius*cos(t),
x@centre[2] + x@radius*sin(t),
type="l", ...)
})
plot(circS4)</lang>
Racket
Racket programs heavily use functions, but classes and objects are available as well:
<lang racket>
- lang racket
(define fish%
(class object% (super-new)
;; an instance variable & constructor argument (init-field size)
;; a new method
(define/public (eat)
(displayln "gulp!"))))
- constructing an instance
(new fish% [size 50]) </lang>
Raku
(formerly Perl 6)
<lang perl6>class Camel { has Int $.humps = 1; }
my Camel $a .= new; say $a.humps; # Automatically generated accessor method.
my Camel $b .= new: humps => 2; say $b.humps;</lang>
A more complex example:
<lang perl6>class Butterfly {
has Int $!age; # With the ! twigil, no public accessor method is generated has Str $.name; has Str $.color; has Bool $.wings;
submethod BUILD(:$!name = 'Camelia', :$!age = 2, :$!color = 'pink') {
# BUILD is called by bless. Its primary use is to to control
# object initialization.
$!wings = $!age > 1;
}
method flap() {
say ($.wings
?? 'Watch out for that hurricane!'
!! 'No wings to flap.');
}
}
my Butterfly $a .= new: age => 5; say "Name: {$a.name}, Color: {$a.color}"; $a.flap;
my Butterfly $b .= new(name => 'Osgood', age => 4); say "Name: {$b.name}, Color: {$b.color}"; $b.flap;</lang>
RapidQ
<lang rapidq>TYPE MyClass EXTENDS QObject
Variable AS INTEGER
CONSTRUCTOR
Variable = 0
END CONSTRUCTOR
SUB someMethod
MyClass.Variable = 1
END SUB
END TYPE
' create an instance DIM instance AS MyClass
' invoke the method instance.someMethod</lang>
Raven
Build classes: <lang raven>class Alpha
'I am Alpha.' as greeting
define say_hello
greeting print
class Beta extend Alpha
'I am Beta!' as greeting</lang>
Execute classes to create objects: <lang raven>Alpha as alpha Beta as beta</lang>
Call methods: <lang raven>alpha.say_hello beta.say_hello</lang>
Result: <lang raven>I am Alpha. I am Beta!</lang>
REALbasic
This class "contains" a number ('TheNumber'). The Number methods allow read and write access to the number, and provide an example of method overloading as well as use of the "Assigns" keyword.
<lang vb> Class NumberContainer
Private TheNumber As Integer Sub Constructor(InitialNumber As Integer) TheNumber = InitialNumber End Sub
Function Number() As Integer Return TheNumber End Function
Sub Number(Assigns NewNumber As Integer) TheNumber = NewNumber End Sub
End Class </lang>
<lang vb> Dim num As New NumberContainer(1) ' call the constructor num.Number = num.Number + 5 ' call both Number methods </lang>
REBOL
<lang REBOL>rebol [
Title: "Classes" URL: http://rosettacode.org/wiki/Classes
]
- Objects are derived from the base 'object!' type. REBOL uses a
- prototyping object system, so any object can be treated as a class,
- from which to derive others.
cowboy: make object! [ name: "Tex" ; Instance variable. hi: does [ ; Method. print [self/name ": Howdy!"]] ]
- I create two instances of the 'cowboy' class.
tex: make cowboy [] roy: make cowboy [ name: "Roy" ; Override 'name' property. ]
print "Say 'hello', boys:" tex/hi roy/hi print ""
- Now I'll subclass 'cowboy'. Subclassing looks a lot like instantiation
legend: make cowboy [ deed: "..." boast: does [ print [self/name ": I once" self/deed "!"]] ]
- Instancing the legend
pecos: make legend [name: "Pecos Bill" deed: "lassoed a twister"]
print "Howdy, Pecos!" pecos/hi print "Tell us about yourself?" pecos/boast</lang>
- Output:
Say 'hello', boys: Tex : Howdy! Roy : Howdy! Howdy, Pecos! Pecos Bill : Howdy! Tell us about yourself? Pecos Bill : I once lassoed a twister !
Ring
Simple program to define class and create an object
<lang ring> New point { x=10 y=20 z=30 print() } Class Point x y z func print see x + nl + y + nl + z + nl </lang>
The previous program can be written in another way
<lang ring> New point # create new object using the point class { # access the new object attributes and methods
x = 10 # set the x attribute to 10
y = 20 # set the y attribute to 20
z = 30 # set the z attribute to 30
print() # call the print method
} # end of object access
Class Point # define the Point class
x y z # the class contains three attributes x, y & z
func print # define the print method
see x + nl + # print the x attribute
y + nl + # print the y attribute
z + nl # print the z attribute
</lang>
Ruby
<lang ruby>class MyClass
def initialize @instance_var = 0 end def add_1 @instance_var += 1 end
end
my_class = MyClass.new #allocates an object and calls it's initialize method, then returns it. </lang>
Rust
<lang rust> struct MyClass {
variable: i32, // member variable = instance variable
}
impl MyClass {
// member function = method, with its implementation
fn some_method(&mut self) {
self.variable = 1;
}
// constructor, with its implementation
fn new() -> MyClass {
// Here could be more code.
MyClass { variable: 0 }
}
}
fn main () {
// Create an instance in the stack. let mut instance = MyClass::new();
// Create an instance in the heap. let mut p_instance = Box::new(MyClass::new());
// Invoke method on both istances, instance.some_method(); p_instance.some_method();
// Both instances are automatically deleted when their scope ends.
} </lang>
Sather
<lang sather>class CLASSTEST is
readonly attr x:INT; -- give a public getter, not a setter private attr y:INT; -- no getter, no setter attr z:INT; -- getter and setter
-- constructor create(x, y, z:INT):CLASSTEST is res :CLASSTEST := new; -- or res ::= new res.x := x; res.y := y; res.z := z; return res; end; -- a getter for the private y summed to s getPrivateY(s:INT):INT is -- y is not shadowed so we can write y instead of -- self.y return y + s; end;
end;</lang>
<lang sather>class MAIN is
main is test ::= #CLASSTEST(1, 2, 3); -- the previous line is syntactic sugar for -- test :CLASSTEST := CLASSTEST::create(1, 2, 3); #OUT + test.z + "\n"; -- we can access z test.z := 25; -- we can set z #OUT + test.x + "\n"; -- we can get x -- test.x := 5; -- we cannot set x #OUT + test.getPrivateY(0) + "\n"; end;
end;</lang>
Scala
Scala can be highly object-oriented and if so the task is trivial. In some cases the constructor and instance variables do not have to be explicitly declared; this example shows two ways each to make constructors and instance variables. <lang Scala>/** This class implicitly includes a constructor which accepts an Int and
* creates "val variable1: Int" with that value. */
class MyClass(val myMethod: Int) { // Acts like a getter, getter automatically generated.
var variable2 = "asdf" // Another instance variable; a public var this time def this() = this(0) // An auxilliary constructor that instantiates with a default value
}
object HelloObject {
val s = "Hello" // Not private, so getter auto-generated
}
/** Demonstrate use of our example class.
*/
object Call_an_object_method extends App {
val s = "Hello" val m = new MyClass() val n = new MyClass(3)
println(HelloObject.s) // prints "Hello" by object getterHelloObject
println(m.myMethod) // prints 0 println(n.myMethod) // prints 3
}</lang>
Scheme
From Structure and Interpretation of Computer Programs <lang Scheme> (define (withdraw amount)
(if (>= balance amount)
(begin (set! balance (- balance amount))
balance)
"Insufficient funds"))
(define (deposit amount)
(set! balance (+ balance amount))
balance)
(define (dispatch m)
(cond ((eq? m 'withdraw) withdraw)
((eq? m 'deposit) deposit)
(else (error "Unknown request -- MAKE-ACCOUNT"
m))))
dispatch)</lang>
Sidef
<lang ruby>class MyClass(instance_var) {
method add(num) {
instance_var += num;
}
}
var obj = MyClass(3); # `instance_var` will be set to 3 obj.add(5); # calls the add() method say obj.instance_var; # prints the value of `instance_var`: 8</lang>
Simula
As the first object-oriented language, Simula introduced both the term class and the object.method(arguments) syntax that many other languages on this page employ. Notice that the object must be declared using ref (reference, i.e. pointer) before it can be instantiated. <lang simula>BEGIN
CLASS MyClass(instanceVariable);
INTEGER instanceVariable;
BEGIN
PROCEDURE doMyMethod(n);
INTEGER n;
BEGIN
Outint(instanceVariable, 5);
Outtext(" + ");
Outint(n, 5);
Outtext(" = ");
Outint(instanceVariable + n, 5);
Outimage
END;
END;
REF(MyClass) myObject;
myObject :- NEW MyClass(5);
myObject.doMyMethod(2)
END</lang>
- Output:
5 + 2 = 7
Slate
Slate objects operate as prototypes with multi-methods: <lang slate>prototypes define: #MyPrototype &parents: {Cloneable} &slots: #(instanceVar). MyPrototype traits addSlot: #classVar.
x@(MyPrototype traits) new [
x clone `>> [instanceVar: 0. ]
].
x@(MyPrototype traits) someMethod [
x instanceVar = 1 /\ (x classVar = 3)
].</lang>
Smalltalk
<lang smalltalk>Object subclass: #MyClass
instanceVariableNames: 'instanceVar' classVariableNames: 'classVar' poolDictionaries: category: 'Testing' !
!MyClass class methodsFor: 'instance creation'! new
^self basicNew instanceVar := 0 ! !
!MyClass methodsFor: 'testing'! someMethod
^self instanceVar = 1; classVar = 3 ! !
MyClass new someMethod!</lang>
SuperCollider
<lang SuperCollider>
SpecialObject {
classvar a = 42, <b = 0, <>c; // Class variables. 42 and 0 are default values. var <>x, <>y; // Instance variables. // Note: variables are private by default. In the above, "<" creates a getter, ">" creates a setter
*new { |value| ^super.new.init(value) // constructor is a class method. typically calls some instance method to set up, here "init" }
init { |value| x = value; y = sqrt(squared(a) + squared(b)) }
// a class method *randomizeAll { a = 42.rand; b = 42.rand; c = 42.rannd; }
// an instance method coordinates { ^Point(x, y) // The "^" means to return the result. If not specified, then the object itself will be returned ("^this") }
}
</lang>
Call it:
<lang SuperCollider> SpecialObject.randomizeAll; a = SpecialObject(8); a.coordinates; </lang>
Swift
<lang swift>class MyClass{
// stored property var variable : Int
/**
* The constructor
*/
init() {
self.variable = 42
}
/**
* A method
*/
func someMethod() {
self.variable = 1
}
}</lang> Instantiate this class using: <lang swift>MyClass()</lang>
Tcl
or
<lang Tcl>package require TclOO oo::class create summation {
variable v
constructor {} {
set v 0
}
method add x {
incr v $x
}
method value {} {
return $v
}
destructor {
puts "Ended with value $v"
}
} set sum [summation new] puts "Start with [$sum value]" for {set i 1} {$i <= 10} {incr i} {
puts "Add $i to get [$sum add $i]"
} $sum destroy</lang>
TIScript
TIScript is prototype-based and yet it has classes. Object that was created as an instance of one class can be transformed to the instance of another class by changing its obj.prototype field.
<lang javascript>class Car {
//Constructor function.
function this(brand, weight, price = 0) {
this.brand = brand;
this.weight = weight || 1000; // Resort to default value (with 'or' notation).
this._price = price;
}
property price(v) // computable property, special kind of member function
{
get { return this._price; } // getter section
set { this._price = v; } // setter section
}
function toString() { // member function, method of a Car.
return String.printf("<%s>",this.brand);
}
}
class Truck : Car {
function this(brand, size) {
super(brand, 2000); // Call of constructor of super class (Car here)
this.size = size; // Custom property for just this object.
}
}
var cars = [ // Some example car objects.
new Car("Mazda"),
new Truck("Volvo", 2, 30000)
]; for (var (i,car) in cars) // TIScript allows enumerate indexes and values {
stdout.printf("#%d %s $%d %v %v, %v %v", i, car.brand, car.price, car.weight, car.size,
car instanceof Car, car instanceof Truck);
}</lang>
- Output:
from console
#1 Mazda 1000 $0 undefined, true false #2 Volvo 2000 $30000 2, true true
TXR
<lang txrlisp>(defstruct shape ()
cached-area
(:init (self) (put-line `@self is born!`))
(:fini (self) (put-line `@self says goodbye!`))
(:method area (self)
(or self.cached-area
(set self.cached-area self.(calc-area)))))
(defstruct circle shape
(radius 1.0)
(:method calc-area (self) (* %pi% self.radius self.radius)))
(defstruct square shape
(length 1.0)
(:method calc-area (self) (* self.length self.length)))</lang>
- Output:
$ txr -i shapes.tl
1> (let ((s (new circle)))
s.(area))
#S(circle cached-area nil radius nil) is born!
3.14159265358979
2> (sys:gc)
#S(circle cached-area 3.14159265358979 radius 1.0) says goodbye!
t
3>
Notes:
defstructandneware macros which compile to invocations of the functionsmake-struct-typeandmake-struct.- The
obj.fun(x, y)syntax is "halfway Lispified", and looks likeobj.(fun x y). This denotes a method call: the functionfunis retrieved from the object, and passed the arguments(obj x y). - The notation
obj.[fun x y]is similar, but will not passobjto fun; it is for calling static functions (class utility functions that don't require an instance). a.b.c.din TXR Lisp is a syntactic sugar for the expression(qref a b c d), where the elements may be compound expressions. Thusobj.(a b).cis(qref obj (a b) c).- There must be no whitespace around the dot:
(a . b)is the consing dot whereas(a.b)is the syntax((qref a b)). - Ambiguity with floating-point numbers isn't allowed. For instance,
a.b.1elicits an error from the parser (lexical scanner actually).
UNIX Shell
ksh93 has "type variables" which essentially declares a class. <lang bash>typeset -T Summation_t=(
integer sum
# the constructor
function create {
_.sum=0
}
# a method
function add {
(( _.sum += $1 ))
}
)
Summation_t s for i in 1 2 3 4 5; do
s.add $i
done print ${s.sum}</lang>
Vala
<lang vala>public class MyClass : Object {
// Instance variable
public int variable;
// Method
public void some_method() {
variable = 24;
}
// Constructor
public MyClass() {
variable = 42;
}
} void main() {
// Class instance
MyClass instance = new MyClass();
print("%d\n", instance.variable);
instance.some_method();
print("%d\n", instance.variable);
instance.variable = 84;
print("%d\n", instance.variable);
}</lang>
VBA
Defining a class
In Visual Basic for Applications a class is defined in a separate Class Module. The name of the class module is the name of the class.
For each property you must supply a "Property Let" routine to set the property (or "Property Set" if the property refers to an object), and a "Property Get" function to get the property.
Methods are represented by Functions in the class module.
A class module can have a constructor - a sub with the special name Class_Initialize - and a destructor with the special name Class_Terminate.
This is the contents of a class module "Foo" (like in the Visual Basic .NET example below):
<lang vb>Private Const m_default = 10 Private m_bar As Integer
Private Sub Class_Initialize()
'constructor, can be used to set default values m_bar = m_default
End Sub
Private Sub Class_Terminate()
'destructor, can be used to do some cleaning up 'here we just print a message Debug.Print "---object destroyed---"
End Sub Property Let Bar(value As Integer)
m_bar = value
End Property
Property Get Bar() As Integer
Bar = m_bar
End Property
Function DoubleBar()
m_bar = m_bar * 2
End Function
Function MultiplyBar(x As Integer)
'another method MultiplyBar = m_bar * x 'Note: instead of using the instance variable m_bar we could refer to the Bar property of this object using the special word "Me": ' MultiplyBar = Me.Bar * x
End Function</lang>
Using an object
Objects (e.g. of class Foo) are created and used in "normal" modules. <lang vb>Public Sub foodemo() 'declare and create separately Dim f As Foo Dim f0 As Foo
Set f = New Foo
'set property f.Bar = 25 'call method f.DoubleBar 'alternative Call f.DoubleBar Debug.Print "f.Bar is "; f.Bar Debug.Print "Five times f.Bar is "; f.MultiplyBar(5)
'declare and create at the same time Dim f2 As New Foo Debug.Print "f2.Bar is "; f2.Bar 'prints default value
'destroy an object Set f = Nothing
'create an object or not, depending on a random number: If Rnd() < 0.5 Then
Set f0 = New Foo
End If 'check if object actually exists If f0 Is Nothing Then
Debug.Print "object f0 does not exist"
Else
Debug.Print "object f0 was created"
End If 'at the end of execution all remaining objects created in this sub will be released. 'this will trigger one or two "object destroyed" messages 'depending on whether f0 was created... End Sub</lang>
- Output:
foodemo f.Bar is 100 Five times f.Bar is 500 f2.Bar is 10 ---object destroyed--- object f0 was created ---object destroyed--- ---object destroyed---
Visual Basic .NET
Defining a class
<lang vbnet>Class Foo
Private m_Bar As Integer
Public Sub New()
End Sub
Public Sub New(ByVal bar As Integer)
m_Bar = bar
End Sub
Public Property Bar() As Integer
Get
Return m_Bar
End Get
Set(ByVal value As Integer)
m_Bar = value
End Set
End Property
Public Sub DoubleBar()
m_Bar *= 2
End Sub
Public Function MultiplyBar(ByVal x As Integer) As Integer
Return x * Bar
End Function
End Class</lang>
Using an object
<lang vbnet>'Declare and create separately Dim foo1 As Foo foo1 = New Foo
'Declare and create at the same time Dim foo2 As New Foo
'... while passing constructor parameters Dim foo3 As New Foo(5)
'... and them immediately set properties Dim foo4 As New Foo With {.Bar = 10}
'Calling a method that returns a value Console.WriteLine(foo4.MultiplyBar(20))
'Calling a method that performs an action foo4.DoubleBar()
'Reading/writing properties Console.WriteLine(foo4.Bar) foo4.Bar = 1000</lang>
Visual FoxPro
Visual FoxPro has a large number of base classes - Session is one of them. <lang vfp> LOCAL o1 As MyClass, o2 As MyClass
- !* Instantiate o1
o1 = NEWOBJECT("MyClass") o1.ShowInstance()
- !* Instantiate o2
o2 = CREATEOBJECT("MyClass", 2) o2.ShowInstance()
DEFINE CLASS MyClass As Session
- !* Custom property (protected)
PROTECTED nInstance nInstance = 0
- !* Constructor
PROCEDURE Init(tnInstance As Integer) IF VARTYPE(tnInstance) = "N"
THIS.nInstance = tnInstance
ELSE
THIS.nInstance = THIS.nInstance + 1
ENDIF ENDPROC
- !* Custom Method
PROCEDURE ShowInstance ? "Instance", THIS.nInstance ENDPROC ENDDEFINE </lang>
- Output:
Instance 1 Instance 2
Wren
<lang ecmascript>class Bear {
// Constructs a Bear instance passing it a name
// which is stored in the field _name
// automatically created by Wren.
construct new(name) { _name = name }
// Property to get the name
name { _name }
// Method to make a noise.
makeNoise() { System.print("Growl!") }
}
// Create a new Bear instance and assign a reference to it // to the variable b. var b = Bear.new("Bruno")
// Print the bear's name. System.print("The bear is called %(b.name).") // Make a noise. b.makeNoise()</lang>
- Output:
The bear is called Bruno. Growl!
X86-64 Assembly
UASM 2.52
Details about the UASM class extention can be found here. <lang asm> option casemap:none
ifndef __SOMECLASS_CLASS__ __SOMECLASS_CLASS__ equ 1
;; Once again, HeapAlloc/Free is REQUIRED by the class extention for windows.
;; Malloc/Free are used by Linux and OSX. So the function prototypes have to
;; be defined somewhere. If you have include files where they're defined, just
;; include them insted in the usual way.
if @Platform eq 1 ;; Windows 64
option dllimport:<kernel32>
;; include windows.inc
;; includelib kernel32.lib
HeapAlloc proto :qword, :dword, :qword
HeapFree proto :qword, :dword, :qword
ExitProcess proto :dword
GetProcessHeap proto
option dllimport:none
exit equ ExitProcess
elseif @Platform eq 3 ;; Linux 64
;;include libc.inc
malloc proto SYSTEMV :qword
free proto SYSTEMV :qword
exit proto SYSTEMV :dword
endif
printf proto :qword, :VARARG
CLASS someClass CMETHOD someMethod ENDMETHODS var dd ? ENDCLASS
pClass typedef ptr someClass
METHOD someClass, Init, <VOIDARG>, <>, a:dword mov rbx, thisPtr assume rbx:ptr someClass mov [rbx].var, a mov rax, rbx assume rbx:nothing ret ENDMETHOD
METHOD someClass, someMethod, <dword>, <> mov rbx, thisPtr assume rbx:ptr someClass mov eax, [rbx].var assume rbx:nothing ret ENDMETHOD
METHOD someClass, Destroy, <VOIDARG>, <> ret ENDMETHOD
endif ;; __CLASS_CLASS_
.code main proc
local meh:ptr someClass
;; Create a new instance of someClass with an arg of 7
mov meh, _NEW(someClass, 7)
meh->someMethod() ;;Get meh->var value and return it in RAX
invoke printf, CSTR("class->someMethod = %i",10), rax
_DELETE(meh) ;; DIIIIIIIE!
invoke exit, 0 ;; Crashy crashy without it.
ret
main endp
end </lang>
- Output:
class->someMethod = 7
XBS
<lang XBS>class Person { construct=func(self,Name,Age,Gender){ self:Name=Name; self:Age=Age; self:Gender=Gender; }{Name="John",Age=20,Gender="Male"}; ToString=func(self){ send self.Name+" ("+self.Gender+"): Age "+self.Age; } }
set John = new Person with []; log(John::ToString()); set Jane = new Person with ["Jane",20,"Female"] log(Jane::ToString());</lang>
- Output:
John (Male): Age 20 Jane (Female): Age 20
XLISP
<lang xlisp>(DEFINE-CLASS PROGRAMMING-LANGUAGE
(INSTANCE-VARIABLES NAME YEAR))
(DEFINE-METHOD (PROGRAMMING-LANGUAGE 'INITIALIZE X)
(SETQ NAME X) SELF)
(DEFINE-METHOD (PROGRAMMING-LANGUAGE 'WAS-CREATED-IN X)
(SETQ YEAR X))
(DEFINE-METHOD (PROGRAMMING-LANGUAGE 'DESCRIBE)
`(THE PROGRAMMING LANGUAGE ,NAME WAS CREATED IN ,YEAR))
(DEFINE LISP (PROGRAMMING-LANGUAGE 'NEW 'LISP))
(LISP 'WAS-CREATED-IN 1958)
(DISPLAY (LISP 'DESCRIBE)) (NEWLINE)</lang>
- Output:
(THE PROGRAMMING LANGUAGE LISP WAS CREATED IN 1958)
zkl
<lang zkl>class C{ // define class named "C", no parents or attributes
println("starting construction"); // all code outside functions is wrapped into the constructor
var v; // instance data for this class
fcn init(x) // initializer for this class, calls constructor
{ v = x }
println("ending construction of ",self);
} c1:=C(5); // create a new instance of C c2:=c1("hoho"); // create another instance of C println(C.v," ",c1.v," ",c2.v);</lang>
- Output:
starting construction ending construction of Class(C) starting construction ending construction of Class(C) Void 5 hoho
<lang zkl>C.__constructor(); // run base class constructor for giggles C.init(456); // initialize base class without creating instance println(C.v," ",c1.v);</lang>
- Output:
starting construction ending construction of Class(C) starting construction ending construction of Class(C) 456 5
zonnon
<lang zonnon> module Graphics; type {ref,public} (* class *) Point = object(ord,abs: integer) var (* instance variables *) {public,immutable} x,y: integer;
(* method *) procedure {public} Ord():integer; begin return y end Ord;
(* method *) procedure {public} Abs():integer; begin return x end Abs;
(* constructor *) begin self.x := ord; self.y := abs; end Point; end Graphics.
module Main; import Graphics; var p: Graphics.Point;
procedure Write(p: Graphics.Point); begin writeln('[':1,p.x:3,',':1,p.y:3,']':1) end Write;
begin p := new Graphics.Point(12,12); Write(p); writeln("Abs: ":4,p.Abs():3," Ord: ":5,p.Ord():3); end Main. </lang>
- Output:
[ 12, 12] Abs: 12 Ord: 12
- Programming Tasks
- Basic language learning
- Object oriented
- Type System
- Encyclopedia
- 11l
- ActionScript
- Ada
- Aikido
- ALGOL 68
- AmigaE
- AutoHotkey
- BaCon
- BASIC
- BBC BASIC
- Blz
- Bracmat
- C
- C sharp
- C++
- Clojure
- COBOL
- Coco
- CoffeeScript
- Common Lisp
- Component Pascal
- Crystal
- D
- Delphi
- DM
- Dragon
- DWScript
- E
- EchoLisp
- Eiffel
- Elena
- ERRE
- F Sharp
- Factor
- Falcon
- Fancy
- Fantom
- Forth
- Fortran
- FreeBASIC
- GLSL
- Go
- Groovy
- Haskell
- Unicon
- J
- Java
- JavaScript
- Julia
- Kotlin
- Lasso
- LFE
- Lingo
- Lisaac
- Logtalk
- Lua
- M2000 Interpreter
- MATLAB
- MiniScript
- Nanoquery
- Nemerle
- NetRexx
- Nim
- Oberon-2
- Objeck
- Object Pascal
- Objective-C
- OCaml
- Oforth
- Ol
- OoRexx
- OxygenBasic
- Oz
- Pascal
- Perl
- Phix
- Phix/Class
- PHL
- PHP
- PicoLisp
- Pop11
- PowerShell
- Processing
- PureBasic
- Python
- R
- Racket
- Raku
- RapidQ
- Raven
- REALbasic
- REBOL
- Ring
- Ruby
- Rust
- Sather
- Scala
- Scheme
- Sidef
- Simula
- Slate
- Smalltalk
- SuperCollider
- Swift
- Tcl
- TclOO
- TIScript
- TXR
- UNIX Shell
- Vala
- VBA
- Visual Basic .NET
- Visual FoxPro
- Wren
- X86-64 Assembly
- XBS
- XLISP
- Zkl
- AWK/Omit
- BASIC/Omit
- Bc/Omit
- Commodore BASIC/Omit
- Dc/Omit
- GUISS/Omit
- Locomotive Basic/Omit
- M4/Omit
- Mathematica/Omit
- Maxima/Omit
- Metafont/Omit
- Modula-2/Omit
- Octave/Omit
- PARI/GP/Omit
- Retro/Omit
- REXX/Omit
- TI-83 BASIC/Omit
- TI-89 BASIC/Omit
- Vim Script/Omit
- ZX Spectrum Basic/Omit
- Zonnon