From: Joel VanderWerf <vjoel@...>
Date: 2006-05-16T07:22:10+09:00
Subject: Re: Mixing-in the inherited method

Christoffer Sawicki wrote:
> Dear Rubyists,
> 
> I fail to understand why the following code doesn't output anything.
> 
> module Foobar
>  def inherited(klass)
>    p klass
>  end
> end
> 
> class Class
>  include Foobar
> end
> 
> class A
> end
> 
> My intuition says it should work since defining Class#inherited
> directly works. I believe I understand the whole "instance methods of
> Class become class methods of Class instances" business, but I must be
> missing something obvious.
> 
> Any ideas?
> 

A is not a subclass of Class, it's an instance of Class.

Also, you need to use extend rather than include, so that the instance
methods of Foobar (particularly, #inherited) become methods of A.
Otherwise, the instance methods of Foobar become instance methods of
_instances_ of A.

These two examples both print "A":

module Foobar
 def inherited(klass)
   p klass
 end
end

class Object
 extend Foobar
end

class A
end

--------------------

module Foobar
 def inherited(klass)
   p klass
 end
end

class Classy
 extend Foobar
end

class A < Classy
end

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407