From: dblack@...
Date: 2002-12-19T03:52:07+09:00
Subject: Re: Mommy, where do methods come from?

Hi --

On Thu, 19 Dec 2002, Chris Pine wrote:

> (Sorry for the subject; couldn't help myself! :)
>
> My (quite serious) question:
>
> Is there a way to tell in which module an object's method was defined?
>
> For example:
>
>   class Foo
>     def to_s; 'foo'; end
>   end
>
>   class Bar; end
>
>   foo = Foo.new
>   bar = Bar.new
>
>   foo.methodClass :to_s  #  Hopefully returns Foo.
>   bar.methodClass :to_s  #  Hopefully returns Object.
>
>
> Furthermore, is there a way to tell all of the modules which did define a
> method for a given object?
>
>   foo.methodClasses :to_s  #  Hopefully returns [Foo, Object].

  class Object
    def mc(meth,mess)
      self.class.ancestors.send(mess) {|mod|
	mod.instance_methods.include?(meth.to_s)
      }
    end

    def method_class(meth)
      mc(meth,:detect)
    end

    def method_classes(meth)
      mc(meth,:select)
    end
  end

  p "".method_class("to_s")          # String
  p Object.new.method_class("to_s")  # Kernel
  p "".method_classes("to_s")        # [String, Kernel]

  class Foo
    def to_s; end
  end

  foo = Foo.new
  p foo.method_classes("to_s")       # [Foo, Kernel]


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav