Send an unknown method call

Invoke an object method where the name of the method to be invoked can be generated at run time.

Cf

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. <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

} </lang>

E

This example goes well with the object named example in Respond to an unknown method call#E.

<lang e>for name in ["foo", "bar"] {

   E.call(example, name, [])

}</lang>

JavaScript

String literal "foo" may be replaced by any expression resulting in a string <lang javascript>example = new Object; example.foo = function(x) {

   return 42 + x;

};

name = "foo"; example[name](5) # => 47</lang>

Objective-C

<lang objc>#import <Foundation/Foundation.h>

@interface Example : NSObject { } - (NSNumber *)foo; @end

@implementation Example - (NSNumber *)foo {

 return [NSNumber numberWithInt:42];

} @end

int main (int argc, const char *argv[]) {

 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

 id example = [[Example alloc] init];
 SEL selector = @selector(foo); // or = NSSelectorFromString(@"foo");
 NSLog(@"%@", [example performSelector:selector withObject:nil]);
 [example release];
 
 [pool release];
 return 0;

}</lang> The performSelector: ... methods can only be used with methods with 0 - 2 object arguments, and an object or void return type. For all other calls, one can create an NSInvocation object and invoke it, or directly call one of the objc_msgSend family of runtime functions.

PARI/GP

Perl

<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"</lang>

Perl 6

Just for the fun of it, we'll mix in an anonymous role into an integer instead of defining a class. <lang perl6>my $object = 42 but role { method add-me($x) { self + $x } } my $name = 'add-me'; say $object."$name"(5); # 47</lang> The double quotes are required, by the way; without them the variable would be interpreted as a hard ref to a method.

PHP

<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"; ?></lang>

PicoLisp

This can be done with the 'send' function. <lang PicoLisp>(send (expression) Obj arg1 arg2)</lang>

Python

String literal "foo" may be replaced by any expression resulting in a string <lang python>class Example(object):

    def foo(self, x):
            return 42 + x

name = "foo" getattr(Example(), name)(5) # => 47</lang>

Qi

<lang qi> (define foo -> 5)

(define execute-function

 Name -> (eval [(INTERN Name)]))

(execute-function "foo") </lang>

Ruby

You may replace :foo, :bar or "bar" with any expression that returns a Symbol or String.

<lang ruby>class Example

 def foo
   42
 end
 def bar(arg1, arg2, &block)
   block.call arg1, arg2
 end

end

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</lang>

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 version 1.9

<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"</lang>

Smalltalk

<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 "</lang>

The perform:with:with: family of methods exist for methods with 0 - 2 (3 in GNU Smalltalk) arguments. For methods with more arguments, use perform:withArguments:, which takes an array of arguments.

Tcl

Method names are really just strings, i.e., ordinary values that can be produced by any mechanism: <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 ...

}</lang> The above produces this output:

42
fee...
fie...
foe...
fum...