From: Trans <transfire@...>
Date: 2005-04-17T01:14:38+09:00
Subject: Re: self


Robert Klemme wrote:
> Oooops... :-)))
>
> Looks like it's rather me that has to go back to school.  Now *you*
explain
> why it works.

Oh dear. Why? Uh.....It just do!

> >> Here's what I do if I want to have a set of singleton methods
> > available for
> >> all classes in a class hierarchy:
> >>
> >> class Base
> >>   module MySpecialClassMethods
> >>     # make inheritance work:
> >>     def inherited(cl) cl.extend MySpecialClassMethods end
> >>
> >>     attr_accessor :bar
> >>     def foo() "foo" end
> >>     # other methods...
> >>   end
> >>
> >>   extend MySpecialClassMethods
> >> end
> >
> > You're right, this is a great approach.
>
> But apparently superfluous
>
> >> class My2 < MyClass
> >>   do_something
> >> end
> success
> => nil
>
> Could it be that this didn't work in older versions?  I'm almost sure
that I
> did try this once and it failed.  This is strange...

Actually I think it always has. But what doesn't is this:

  module MyNotSoSuperModule
    def self.do_something
      puts "success"
    end
  end

 class MyClass
   include MyNotSoSuperModule
   do_something
 end

#=> undefined local variable or method `do_something' for MyClass:Class
(NameError)

Maybe you got the cases crossed? Actually I got them crossed myself, as
I was thinking your example did us this service by allowing modules to
include class-level methods, but that would actually require using
#included rather then #inherited, like this:

  module Base
    module MySpecialClassMethods
      # make inheritance work:
      def included(cl)
        cl.extend MySpecialClassMethods
        p self, cl
      end

      attr_accessor :bar
      def foo() "foo" end
      # other methods...
    end

    extend MySpecialClassMethods
  end

  class Derived
    include Base
  end

  p Derived.foo

  class Derived2 < Derived
  end

  p Derived2.foo

And that is a good idea, I think.

> Thanks for crushing my certainty!

Hey, no problem. I'm an expert at crushing my own, so the least I could
do was share :-)
 
T.