From: Rick DeNatale <rick.denatale@...>
Date: 2007-03-07T06:59:02+09:00
Subject: Re: Metaprogramming and module question

On 3/6/07, Phrogz <gavin@refinery.com> wrote:
> On Mar 6, 2:24 pm, "Pedro Del Gallego" <pedro.delgall...@gmail.com>
> wrote:
> > but i ve a proble when i try to move the pre and post method to a
> > module. Can anyone explainme why the pre methods is  undefined in the
> > class ?
> [snip]
>
> Including a Module into a Class only links in the 'instance' methods
> of that module as instance methods of the class. Module methods (def
> self.foo) are not inherited as 'class' methods.
>
> See http://phrogz.net/RubyLibs/RubyMethodLookupFlow.png for a visual
> explanation.
>
> The easiest thing to do is make those methods instance methods of the
> module, and extend your Song class with them

And a good way to do this automatically and make including the
MetaTest module  do what the OP expects is something like:

module MetaTest

  def self.included(mod)
    puts "and now  MetaTest has been used by #{mod.inspect}..."
    mod.extend(ClassMethods)
  end

  module ClassMethods

    def pre (name_method, &condition)
      old_method = instance_method(name_method)

      define_method(name_method)  { |*args|
	condition.call
	old_method.bind(self).call(*args)
      }
    end

    def post (name_method, &condition)
      old_method = instance_method(name_method)

      define_method(name_method)  { |*args|
	condition.call
      }
    end
  end
end


-- 
Rick DeNatale

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