Send an unknown method call

Send an unknown method call is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

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

Cf

• Respond to an unknown method call.
• Runtime evaluation

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.

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

<lang perl6>$object."$methname"(5)</lang>

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>

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>

Ruby

<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</lang>