From: Jeff Rose <rosejn@...>
Date: 2006-06-08T20:42:01+09:00
Subject: Re: Why the lack of mixing-in support for Class methods?

Alder Green wrote:
> Hi
> 
> I'm confused as to why class methods aren't include'd by default along
> with instance methods when mixing-in modules.
> 
> It obstructs the important orthoganility between modules and classes,
> and - among other problems - thus undermines the position of mixins as
> an alternative to class-based multiple inheritance.
> 
> In short, I can see a lot of poor consequence to that lack of support,
> while on the other hand no good reason for it. Maybe someone would
> care to elighten me?
> 
> (I'm aware of the various hacks for fudging such support, and in fact
> use some of them in my code. But there are readability and
> maintainability issues with those hacks for something that's supposed
> to be a core feature).
> 


You can do this without too much trouble.  This is what I use, which is 
based off some code _why posted on his blog a while back.

---- meta.rb ----


# A set of methods to help create meta-programming gizmos.
class Object
   # The metaclass is the singleton behind every object.
   def metaclass
     class << self
       self
     end
   end

   # Evaluates the block in the context of the metaclass
   def meta_eval &blk
     metaclass.instance_eval &blk
   end

   # Acts like an include except it adds the module's methods
   # to the metaclass so they act like class methods.
   def meta_include mod
     meta_eval do
       include mod
     end
   end

   # Adds methods to a metaclass
   def meta_def name, &blk
     meta_eval { define_method name, &blk }
   end

   # Defines an instance method within a class
   def class_def name, &blk
     class_eval { define_method name, &blk }
   end
end

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

require 'meta'

module Foo
   def test
     puts "test method"
   end
end

class Bar
   meta_include Foo
end

Bar.test
# >> "test method\n"


-Jeff