From: Rick DeNatale <rick.denatale@...>
Date: 2007-03-24T03:26:03+09:00
Subject: Re: What is the problem with this module function.

On 3/22/07, Phrogz <gavin@refinery.com> wrote:

> Ruby looks in E, then D, then M, then C, then B, then A. The reason
> (or at least a reason that makes sense to me) is:
>
> a) Look in yourself before you look any higher.
> b) Modules explicitly included in yourself are more important than
> your superclass.

This is in general true, however, there's a quirk,

module M
  def foo
       p 'M::foo'
  end
end

class A
    include M
end

class B < A
    def foo
        p 'B::foo'
    end
end

class C < B
     include M
end

Now for the quiz

A.new.foo  ==> "M::foo"
B.new.foo ==> "B::foo"
C.new.foo ==> ?

Now you might expect that since C explicitly re-included M that it should be
"M::foo",  however instead it's "B::foo".

I know why this happens based on what the implementation of module
inclusion does, I don't understand WHY it does it that way.  It's just
the way it is.

For a time, Ruby1.9 allowed re-inclusion of a module by a subclass and
C.new.foo DID return "M::foo", but for some reason, the current 1.9
(or at least the latest version I've gotten from SVN) has gone back to
the old behavior.

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/