Send an unknown method call: Difference between revisions
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{{
;Task:
Invoke an object method where the name of the method to be invoked can be generated at run time.
;Related tasks:
* [[Respond to an unknown method call]].
* [[Runtime evaluation]]
<br><br>
=={{header|AutoHotkey}}==
This object has 3 methods, and asks the user to name one to call. Instead of using Func(), one could use a class definition.
<syntaxhighlight lang="ahk">obj := {mA: Func("mA"), mB: Func("mB"), mC: Func("mC")}
InputBox, methodToCall, , Which method should I call?
obj[methodToCall].()
mA(){
MsgBox Method A
}
mB(){
MsgBox Method B
}
mC(){
MsgBox Method C
}
</syntaxhighlight>
=={{header|Bracmat}}==
<syntaxhighlight lang="bracmat">(task=
( oracle
= (predicate="is made of green cheese")
(generateTruth=.str$(!arg " " !(its.predicate) "."))
(generateLie=.str$(!arg " " !(its.predicate) "!"))
)
& new$oracle:?SourceOfKnowledge
& put
$ "You may ask the Source of Eternal Wisdom ONE thing.
Enter \"Truth\" or \"Lie\" on the next line and press the <Enter> key.
"
& whl
' ( get':?trueorlie:~Truth:~Lie
& put$"Try again\n"
)
& put$(str$("You want a " !trueorlie ". About what?" \n))
& get'(,STR):?something
& (SourceOfKnowledge..str$(generate !trueorlie))$!something
);
</syntaxhighlight>
{{out|Example}}
<pre>{?} !task
You may ask the Source of Eternal Wisdom ONE thing.
Enter "Truth" or "Lie" on the next line and press the <Enter> key.
"Lie"
You want a Lie. About what?
The sea
{!} The sea is made of green cheese!</pre>
=={{header|C sharp|C#}}==
<syntaxhighlight lang="csharp">using System;
class Example
{
public int foo(int x)
{
return 42 + x;
}
}
class Program
{
static void Main(string[] args)
{
var example = new Example();
var method = "foo";
var result = (int)example.GetType().GetMethod(method).Invoke(example, new object[]{ 5 });
Console.WriteLine("{0}(5) = {1}", method, result);
}
}
</syntaxhighlight>
{{out}}
foo(5) = 47
=={{header|Caché ObjectScript}}==
$METHOD executes a named instance method for a specified instance of a designated class.
<syntaxhighlight lang="cos">Class Unknown.Example Extends %RegisteredObject
{
Method Foo()
{
Write "This is foo", !
}
Method Bar()
{
Write "This is bar", !
}
}</syntaxhighlight>
{{out|Examples}}
<pre>
USER>Set obj=##class(Unknown.Example).%New()
USER>Do $Method(obj, "Foo")
This is foo
USER>Do $Method(obj, "Bar")
This is bar
</pre>
=={{header|Clojure}}==
<syntaxhighlight lang="clojure">
(import '[java.util Date])
(import '[clojure.lang Reflector])
(def date1 (Date.))
(def date2 (Date.))
(def method "equals")
;; Two ways of invoking method "equals" on object date1
;; using date2 as argument
;; Way 1 - Using Reflector class
;; NOTE: The argument date2 is passed inside an array
(Reflector/invokeMethod date1 method (object-array [date2]))
;; Way 2 - Using eval
;; Eval runs any piece of valid Clojure code
;; So first we construct a piece of code to do what we want (where method name is inserted dynamically),
;; then we run the code using eval
(eval `(. date1 ~(symbol method) date2))
</syntaxhighlight>
=={{header|Common Lisp}}==
Unknown methods are called just like any other function. Find the method-naming symbol using INTERN then call it with FUNCALL.
<syntaxhighlight lang="lisp">(funcall (intern "SOME-METHOD") my-object a few arguments)</syntaxhighlight>
=={{header|Déjà Vu}}==
<syntaxhighlight lang="dejavu">local :object { :add @+ }
local :method :add
!. object! method 1 2</syntaxhighlight>
{{out}}
<pre>3</pre>
=={{header|E}}==
This example goes well with the object named <code>example</code> in [[Respond to an unknown method call#E]].
<syntaxhighlight lang="e">for name in ["foo", "bar"] {
E.call(example, name, [])
}</syntaxhighlight>
=={{header|Ecstasy}}==
Here's a simple example of a test module using its runtime type to search for methods by some name (specified on the the command line), grabbing the one by that name that requires no parameters, and dynamically invoking it:
<syntaxhighlight lang="ecstasy">
module test {
@Inject Console console;
void run(String[] args) {
String name = args.empty ? "foo" : args[0];
if (val mm := &this.actualType.multimethods.get(name),
val m := mm.methods.any(m -> m.ParamTypes.size == 0)) {
m.invoke(this, Tuple:());
} else {
console.print($"No such 0-parameter method: {name.quoted()}");
}
}
void foo() {
console.print("this is the foo() method");
}
void bar() {
console.print("this is the bar() method");
}
}
</syntaxhighlight>
{{out}}
<pre>
x$ xec test foo
this is the foo() method
x$ xec test bar
this is the bar() method
x$ xec test baz
No such 0-parameter method: "baz"
</pre>
=={{header|Elena}}==
ELENA 4.1 :
<syntaxhighlight lang="elena">import extensions;
class Example
{
foo(x)
= x + 42;
}
public program()
{
var example := new Example();
var methodSignature := "foo";
var invoker := new MessageName(methodSignature);
var result := invoker(example,5);
console.printLine(methodSignature,"(",5,") = ",result)
}</syntaxhighlight>
{{out}}
<pre>
foo(5) = 47
</pre>
=={{header|Factor}}==
Factor's object model is such that objects themselves don't contain methods — generic words do. So there is nothing different about invoking an unknown method than invoking an unknown word in general.
<syntaxhighlight lang="factor">USING: accessors kernel math prettyprint sequences words ;
IN: rosetta-code.unknown-method-call
TUPLE: foo num ;
C: <foo> foo
GENERIC: add5 ( x -- y )
M: foo add5 num>> 5 + ;
42 <foo> ! construct a foo
"add" "5" append ! construct a word name
! must specify vocab to look up a word
"rosetta-code.unknown-method-call"
lookup-word execute . ! 47</syntaxhighlight>
=={{header|Forth}}==
{{works with|Forth}}
Works with any ANS Forth
Needs the FMS-SI (single inheritance) library code located here:
http://soton.mpeforth.com/flag/fms/index.html
<syntaxhighlight lang="forth">include FMS-SI.f
include FMS-SILib.f
var x \ instantiate a class var object named x
\ Use a standard Forth string and evaluate it.
\ This is equivalent to sending the !: message to object x
42 x s" !:" evaluate
x p: 42 \ send the print message ( p: ) to x to verify the contents
</syntaxhighlight>
=={{header|FreeBASIC}}==
<syntaxhighlight lang="basic">Type Example
foo As Integer Ptr
Declare Constructor (x As Integer)
End Type
Constructor Example(x As Integer)
This.foo = New Integer
*This.foo = 42 + x
End Constructor
Dim As Example result = 5
Print *result.foo
Sleep</syntaxhighlight>
{{out}}
<pre> 47</pre>
=={{header|Go}}==
<syntaxhighlight lang="go">package main
import (
"fmt"
"reflect"
)
type example struct{}
// the method must be exported to be accessed through reflection.
func (example) Foo() int {
return 42
}
func main() {
// create an object with a method
var e example
// get the method by name
m := reflect.ValueOf(e).MethodByName("Foo")
// call the method with no argments
r := m.Call(nil)
// interpret first return value as int
fmt.Println(r[0].Int()) // => 42
}</syntaxhighlight>
=={{header|Groovy}}==
<syntaxhighlight lang="grrovy">class Example {
def foo(value) {
"Invoked with '$value'"
}
}
def example = new Example()
def method = "foo"
def arg = "test value"
assert "Invoked with 'test value'" == example."$method"(arg)</syntaxhighlight>
==Icon and {{header|Unicon}}==
<syntaxhighlight lang="unicon">procedure main()
x := foo() # create object
x.m1() # static call of m1 method
# two examples where the method string can be dynamically constructed ...
"foo_m1"(x) # ... need to know class name and method name to construct name
x.__m["m1"] # ... general method (better)
end
class foo(a,b,c) # define object
method m1(x)
end
end</syntaxhighlight>
For more information on this see [[Respond_to_an_unknown_method_call#Icon_and_Unicon|Respond to an unknown method call]].
=={{header|Io}}==
String literal "foo" may be replaced by any expression resulting in a string.
<syntaxhighlight lang="io">Example := Object clone
Example foo := method(x, 42+x)
name := "foo"
Example clone perform(name,5) println // prints "47"</syntaxhighlight>
=={{header|J}}==
'''Solution''': There are multiple ways to evoke code at runtime. The most common is '''<tt>". y</tt>''' (''eval''uate the code in the string y, producing a noun), but there's also <tt>'name'~ </tt> (which will modify J's stack by replacing the two tokens '''<tt>'name'</tt>''' and <tt>~</tt> with the named object) as well as '''<tt>x 128!:2 y</tt>''' (''apply'' the verb described by <tt>x</tt> to the noun <tt>y</tt>).
There are other methods as well, e.g., '''<tt>@.</tt>''','''<tt>`:</tt>''', and '''<tt>^:</tt>''', though these are designed to consume gerunds (pre-parsed ASTs) rather than strings (though, of course, a pre-processor can always be provided to convert strings into ASTs before feeding them to these operators).
'''Example''':<syntaxhighlight lang="j"> sum =: +/
prod =: */
count =: #
nameToDispatch =: 'sum' NB. pick a name already defined
". nameToDispatch,' 1 2 3'
6
nameToDispatch~ 1 2 3
6
nameToDispatch (128!:2) 1 2 3
6
nameToDispatch =: 'count' NB. pick another name
". nameToDispatch,' 1 2 3'
3
nameToDispatch~ 1 2 3
3
nameToDispatch (128!:2) 1 2 3
3</syntaxhighlight>
=={{header|Java}}==
Using reflection
<syntaxhighlight lang="java">import java.lang.reflect.Method;
class Example {
public int foo(int x) {
return 42 + x;
}
}
public class Main {
public static void main(String[] args) throws Exception {
Object example = new Example();
String name = "foo";
Class<?> clazz = example.getClass();
Method meth = clazz.getMethod(name, int.class);
Object result = meth.invoke(example, 5); // result is int wrapped in an object (Integer)
System.out.println(result); // prints "47"
}
}</syntaxhighlight>
=={{header|JavaScript}}==
String literal "foo" may be replaced by any expression resulting in a string
<syntaxhighlight lang="javascript">example = new Object;
example.foo = function(x) {
return 42 + x;
};
name = "foo";
example[name](5) # => 47</syntaxhighlight>
=={{header|Julia}}==
{{works with|Julia|0.6}}
<syntaxhighlight lang="julia">const functions = Dict{String,Function}(
"foo" => x -> 42 + x,
"bar" => x -> 42 * x)
@show functions["foo"](3)
@show functions["bar"](3)</syntaxhighlight>
{{out}}
<pre>(functions["foo"])(3) = 45
(functions["bar"])(3) = 126</pre>
=={{header|Kotlin}}==
When you try to compile the following program, it will appear to the compiler that the local variable 'c' is assigned but never used and a warning will be issued accordingly. You can get rid of this warning by compiling using the -nowarn flag.
<syntaxhighlight lang="scala">// Kotlin JS version 1.1.4-3
class C {
fun foo() {
println("foo called")
}
}
fun main(args: Array<String>) {
val c = C()
val f = "c.foo"
js(f)() // invokes c.foo dynamically
}</syntaxhighlight>
{{out}}
<pre>
foo called
</pre>
=={{header|Lasso}}==
<syntaxhighlight lang="lasso">define mytype => type {
public foo() => {
return 'foo was called'
}
public bar() => {
return 'this time is was bar'
}
}
local(obj = mytype, methodname = tag('foo'), methodname2 = tag('bar'))
#obj->\#methodname->invoke
#obj->\#methodname2->invoke</syntaxhighlight>
{{out}}
<pre>foo was called
this time is was bar</pre>
=={{header|Lingo}}==
<syntaxhighlight lang="lingo">obj = script("MyClass").new()
-- ...
method = #foo
arg1 = 23
res = call(method, obj, arg1)</syntaxhighlight>
=={{header|Logtalk}}==
For this task, we first define a simple object with a single method:
<syntaxhighlight lang="logtalk">:- object(foo).
:- public(bar/1).
bar(42).
:- end_object.</syntaxhighlight>Second, we define another object that asks the user for a message to be sent to the first object:<syntaxhighlight lang="logtalk">
:- object(query_foo).
:- public(query/0).
query :-
write('Message: '),
read(Message),
foo::Message.
write('Reply: '),
write(Message), nl.
:- end_object.</syntaxhighlight>After compiling and loading both objects, we can try:
| ?- query_foo::query.
Message: bar(X).
Reply: bar(42)
=={{header|Lua}}==
Don't forget to pass the object for methods!
<syntaxhighlight lang="lua">local example = { }
function example:foo (x) return 42 + x end
local name = "foo"
example[name](example, 5) --> 47</syntaxhighlight>
=={{header|Mathematica}}/{{header|Wolfram Language}}==
Creates a dialog box where one can type a function (Sin, Cos, Tan ...) and then a second dialog box for a value.
<syntaxhighlight lang="text">ToExpression[Input["function? E.g. Sin",]][Input["value? E.g. 0.4123"]]</syntaxhighlight>
{{out}}
<pre>Input: Sin
Input: 3.1415
Output: 0.0000926536</pre>
=={{header|MATLAB}} / {{header|Octave}}==
<syntaxhighlight lang="matlab">
funName = 'foo'; % generate function name
feval (funNAME, ...) % evaluation function with optional parameters
funName = 'a=atan(pi)'; % generate function name
eval (funName, 'printf(''Error\n'')')
</syntaxhighlight>
=={{header|Objective-C}}==
<syntaxhighlight lang="objc">#import <Foundation/Foundation.h>
@interface Example : NSObject
- (NSNumber *)foo;
@end
@implementation Example
- (NSNumber *)foo {
return @42;
}
@end
int main (int argc, const char *argv[]) {
@autoreleasepool {
id example = [[Example alloc] init];
SEL selector = @selector(foo); // or = NSSelectorFromString(@"foo");
NSLog(@"%@", [example performSelector:selector]);
}
return 0;
}</syntaxhighlight>
The <code>performSelector: ...</code> methods can only be used with methods with 0 - 2 object arguments, and an object or <code>void</code> return type. For all other calls, one can create an <code>NSInvocation</code> object and invoke it, or directly call one of the <code>objc_msgSend</code> family of runtime functions.
=={{header|Oforth}}==
A method object can be retrieved from its name using asMethod.
<syntaxhighlight lang="oforth">16 "sqrt" asMethod perform</syntaxhighlight>
Others :
asFuntion : retrieve a function
asClass : retrieve a class
asProperty : retrieve a property
A generic way to search a word into the dictionary in to use find method :
<syntaxhighlight lang="oforth">16 "sqrt" Word find perform</syntaxhighlight>
=={{header|PARI/GP}}==
<syntaxhighlight lang="parigp">foo()=5;
eval(Str("foo","()"))</syntaxhighlight>
=={{header|Pascal}}==
Works with FPC (tested with version 3.2.2).
In the simplest case, when the methods are procedures without parameters, it might look something like this (note that these methods are currently required to have PUBLISHED visibility):
<syntaxhighlight lang="pascal">
program Test;
{$mode objfpc}{$h+}
uses
SysUtils;
type
TProc = procedure of object;
{$push}{$m+}
TMyObj = class
strict private
FName: string;
public
constructor Create(const aName: string);
property Name: string read FName;
published
procedure Foo;
procedure Bar;
end;
{$pop}
constructor TMyObj.Create(const aName: string);
begin
FName := aName;
end;
procedure TMyObj.Foo;
begin
WriteLn(Format('This is %s.Foo()', [Name]));
end;
procedure TMyObj.Bar;
begin
WriteLn(Format('This is %s.Bar()', [Name]));
end;
procedure CallByName(o: TMyObj; const aName: string);
var
m: TMethod;
begin
m.Code := o.MethodAddress(aName);
if m.Code <> nil then begin
m.Data := o;
TProc(m)();
end else
WriteLn(Format('Unknown method(%s)', [aName]));
end;
var
o: TMyObj;
begin
o := TMyObj.Create('Obj');
CallByName(o, 'Bar');
CallByName(o, 'Foo');
CallByName(o, 'Baz');
o.Free;
end.
</syntaxhighlight>
{{out}}
<pre>
This is Obj.Bar()
This is Obj.Foo()
Unknown method(Baz)
</pre>
=={{header|Perl}}==
<syntaxhighlight lang="perl">package Example;
sub new {
bless {}
}
sub foo {
my ($self, $x) = @_;
return 42 + $x;
}
package main;
my $name = "foo";
print Example->new->$name(5), "\n"; # prints "47"</syntaxhighlight>
=={{header|Phix}}==
Not specifically anything to do with objects, but you can construct routine names at runtime:
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">Hello</span><span style="color: #0000FF;">()</span>
<span style="color: #0000FF;">?</span><span style="color: #008000;">"Hello"</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">erm</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">"Hemmm"</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">3</span> <span style="color: #008080;">to</span> <span style="color: #000000;">5</span> <span style="color: #008080;">do</span>
<span style="color: #000000;">erm</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]+=-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">+(</span><span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">5</span><span style="color: #0000FF;">)*</span><span style="color: #000000;">3</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #7060A8;">call_proc</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">routine_id</span><span style="color: #0000FF;">(</span><span style="color: #000000;">erm</span><span style="color: #0000FF;">),{})</span>
<!--</syntaxhighlight>-->
=={{header|PHP}}==
<syntaxhighlight lang="php"><?php
class Example {
function foo($x) {
return 42 + $x;
}
}
$example = new Example();
$name = 'foo';
echo $example->$name(5), "\n"; // prints "47"
// alternately:
echo call_user_func(array($example, $name), 5), "\n";
?></syntaxhighlight>
=={{header|Picat}}==
For functions use <code>apply/n</code> and for predicates <code>call/n</code>. The name of the function/predicate must be an atom and strings must be converted to atom, e.g. with <code>to_atom/1</code>.
<syntaxhighlight lang="picat">go =>
println("Function: Use apply/n"),
Fun = "fib",
A = 10,
% Convert F to an atom
println(apply(to_atom(Fun),A)),
nl,
println("Predicate: use call/n"),
Pred = "pyth",
call(Pred.to_atom,3,4,Z),
println(z=Z),
% Pred2 is an atom so it can be used directly with call/n.
Pred2 = pyth,
call(Pred.to_atom,13,14,Z2),
println(z2=Z2),
nl.
% A function
fib(1) = 1.
fib(2) = 1.
fib(N) = fib(N-1) + fib(N-2).
% A predicate
pyth(X,Y,Z) =>
Z = X**2 + Y**2.</syntaxhighlight>
{{out}}
<pre>Function: Use apply/n
55
Predicate: use call/n
z = 25
z2 = 365</pre>
=={{header|PicoLisp}}==
This can be done with the '[http://software-lab.de/doc/refS.html#send send]' function.
<syntaxhighlight lang="picolisp">(send (expression) Obj arg1 arg2)</syntaxhighlight>
=={{header|Pike}}==
with [] instead of -> a string can be used to name a method:
<syntaxhighlight lang="pike">string unknown = "format_nice";
object now = Calendar.now();
now[unknown]();</syntaxhighlight>
=={{header|PowerShell}}==
A random method using a random number:
<syntaxhighlight lang="powershell">
$method = ([Math] | Get-Member -MemberType Method -Static | Where-Object {$_.Definition.Split(',').Count -eq 1} | Get-Random).Name
$number = (1..9 | Get-Random) / 10
$result = [Math]::$method($number)
$output = [PSCustomObject]@{
Method = $method
Number = $number
Result = $result
}
$output | Format-List
</syntaxhighlight>
{{Out}}
<pre>
Method : Atan
Number : 0.5
Result : 0.463647609000806
</pre>
=={{header|Python}}==
String literal "foo" may be replaced by any expression resulting in a string
<
def foo(self, x):
return 42 + x
name = "foo"
getattr(Example(), name)(5) # => 47</
=={{header|Qi}}==
<syntaxhighlight lang="qi">
(define foo -> 5)
(define execute-function
Name -> (eval [(INTERN Name)]))
(execute-function "foo")
</syntaxhighlight>
=={{header|Racket}}==
<syntaxhighlight lang="racket">
#lang racket
(define greeter
(new (class object% (super-new)
(define/public (hello name)
(displayln (~a "Hello " name "."))))))
; normal method call
(send greeter hello "World")
; sending an unknown method
(define unknown 'hello)
(dynamic-send greeter unknown "World")
</syntaxhighlight>
=={{header|Raku}}==
(formerly Perl 6)
Just for the fun of it, we'll mix in an anonymous role into an integer instead of defining a class.
<syntaxhighlight lang="raku" line>my $object = 42 but role { method add-me($x) { self + $x } }
my $name = 'add-me';
say $object."$name"(5); # 47</syntaxhighlight>
The double quotes are required, by the way; without them the variable would be interpreted as a hard ref to a method.
=={{header|Ruby}}==
You may replace :foo, :bar or "bar" with any expression that returns a Symbol or String.
<syntaxhighlight lang="ruby">class Example
def foo
42
Line 28 ⟶ 788:
symbol = :foo
Example.new.send symbol # => 42
Example.new.send( :bar, 1, 2 ) { |x,y| x+y } # => 3
args = [1, 2]
Example.new.send( "bar", *args ) { |x,y| x+y } # => 3</syntaxhighlight>
Object#send can also call protected and private methods, skipping the usual access checks. Ruby 1.9 adds Object#public_send, which only calls public methods.
{{works with|Ruby|1.9}}
<syntaxhighlight lang="ruby">class Example
private
def privacy; "secret"; end
public
def publicity; "hi"; end
end
e = Example.new
e.public_send :publicity # => "hi"
e.public_send :privacy # raises NoMethodError
e.send :privacy # => "secret"</syntaxhighlight>
=={{header|Scala}}==
{{libheader|Scala}}<syntaxhighlight lang="scala">class Example {
def foo(x: Int): Int = 42 + x
}
object Main extends App {
val example = new Example
val meth = example.getClass.getMethod("foo", classOf[Int])
assert(meth.invoke(example, 5.asInstanceOf[AnyRef]) == 47.asInstanceOf[AnyRef], "Not confirm expectation.")
println(s"Successfully completed without errors. [total ${scala.compat.Platform.currentTime - executionStart} ms]")
}</syntaxhighlight>
=={{header|Sidef}}==
<syntaxhighlight lang="ruby">class Example {
method foo(x) {
42 + x
}
}
var name = 'foo'
var obj = Example()
say obj.(name)(5) # prints: 47
say obj.method(name)(5) # =//=</syntaxhighlight>
=={{header|Smalltalk}}==
<syntaxhighlight lang="smalltalk">Object subclass: #Example.
Example extend [
foo: x [
^ 42 + x ] ].
symbol := 'foo:' asSymbol. " same as symbol := #foo: "
Example new perform: symbol with: 5. " returns 47 "</syntaxhighlight>
The <code>perform:with:with:</code> family of methods exist for methods with 0 - 2 (3 in [[GNU Smalltalk]]) arguments. For methods with more arguments, use <code>perform:withArguments:</code>, which takes an array of arguments.
=={{header|Swift}}==
Generally speaking, pure Swift is a very statically typed language, and calling unknown methods is impossible. However, Swift provides a few ways in which instances of specially marked objects can receive unknown method calls.
===Objective-C Compatibility Using @objc===
The first case is used for interfacing with legacy Objective-C libraries. Objective-C is heavily dynamic with Smalltalk-style message passing. So Swift must be able to participate in this.
<syntaxhighlight lang="swift">import Foundation
class MyUglyClass: NSObject {
@objc
func myUglyFunction() {
print("called myUglyFunction")
}
}
let someObject: NSObject = MyUglyClass()
someObject.perform(NSSelectorFromString("myUglyFunction"))</syntaxhighlight>
{{out}}
<pre>called myUglyFunction</pre>
===Dynamic Language Interop with @dynamicCallable and @dynamicMemberLookup===
One of Swift's goals is to able to effectively bridge to dynamic languages such as Python and JavaScript. In order to facilitate more natural APIs, Swift provides the <code>@dynamicCallable</code> and <code>@dynamicMemberLookup</code> attributes which allow for runtime handling of method calls.
<syntaxhighlight lang="swift">@dynamicCallable
protocol FunDynamics {
var parent: MyDynamicThing { get }
func dynamicallyCall(withArguments args: [Int]) -> MyDynamicThing
func dynamicallyCall(withKeywordArguments args: [String: Int]) -> MyDynamicThing
}
extension FunDynamics {
func dynamicallyCall(withKeywordArguments args: [String: Int]) -> MyDynamicThing {
if let add = args["adding"] {
parent.n += add
}
if let sub = args["subtracting"] {
parent.n -= sub
}
return parent
}
}
@dynamicMemberLookup
class MyDynamicThing {
var n: Int
init(n: Int) {
self.n = n
}
subscript(dynamicMember member: String) -> FunDynamics {
switch member {
case "subtract":
return Subtracter(parent: self)
case "add":
return Adder(parent: self)
case _:
return Nuller(parent: self)
}
}
}
struct Nuller: FunDynamics {
var parent: MyDynamicThing
func dynamicallyCall(withArguments args: [Int]) -> MyDynamicThing { parent }
}
struct Subtracter: FunDynamics {
var parent: MyDynamicThing
func dynamicallyCall(withArguments args: [Int]) -> MyDynamicThing {
switch args.count {
case 1:
parent.n -= args[0]
case _:
print("Unknown call")
}
return parent
}
}
struct Adder: FunDynamics {
var parent: MyDynamicThing
func dynamicallyCall(withArguments arg: [Int]) -> MyDynamicThing {
switch arg.count {
case 1:
parent.n += arg[0]
case _:
print("Unknown call")
}
return parent
}
}
let thing =
MyDynamicThing(n: 0)
.add(20)
.divide(2) // Unhandled call, do nothing
.subtract(adding: 10, subtracting: 14)
print(thing.n)</syntaxhighlight>
{{out}}
<pre>16</pre>
=={{header|Tcl}}==
Method names are really just strings, i.e., ordinary values that can be produced by any mechanism:
<syntaxhighlight lang="tcl">package require Tcl 8.6
oo::class create Example {
method foo {} {return 42}
method 1 {s} {puts "fee$s"}
method 2 {s} {puts "fie$s"}
method 3 {s} {puts "foe$s"}
method 4 {s} {puts "fum$s"}
}
set eg [Example new]
set mthd [format "%c%c%c" 102 111 111]; # A "foo" by any other means would smell as sweet
puts [$eg $mthd]
for {set i 1} {$i <= 4} {incr i} {
$eg $i ...
}</syntaxhighlight>
{{out|The above produces this output}}
42
fee...
fie...
foe...
fum...
=={{header|Wren}}==
<syntaxhighlight lang="wren">import "meta" for Meta
class Test {
construct new() {}
foo() { System.print("Foo called.") }
bar() { System.print("Bar called.") }
}
var test = Test.new()
for (method in ["foo", "bar"]) {
Meta.eval("test.%(method)()")
}</syntaxhighlight>
{{out}}
<pre>
Foo called.
Bar called.
</pre>
=={{header|zkl}}==
<syntaxhighlight lang="zkl">name:="len"; "this is a test".resolve(name)() //-->14</syntaxhighlight>
{{omit from|Ada}}
{{omit from|Axe}}
{{omit from|BASIC}}
{{omit from|C|No such thing as object method}}
{{omit from|C++}}
{{omit from|GUISS}}
{{omit from|Nim}}
{{omit from|Rust|No runtime reflection}}
{{omit from|ZX Spectrum Basic}}
| |||