From: Adam Salter <adam.q.salter@...>
Date: 2007-12-13T08:15:08+09:00
Subject: Inheritance and meta-classes

Hi all,

OK. I'm trying to work out where a method is defined in Rails.
It's in a test, and the specific function that's being called is  
'post', but my question is not a Rails question, it's Ruby.

How do I find where a function is defined in the inheritance tree?
Because of metaclass inheritance being cyclical I don't know where to  
stop looking.

I made the following as a test but I still can't find the function  
being called so I'm guessing I'm missing some of the inheritance tree...

module Debugs
   def find_respond_to_in_class_heirarchy(obj, method)
     if obj.respond_to?(:superclass)
       arr = find_respond_to_in_class_heirarchy(obj.superclass, method)
       arr.unshift([obj.class.respond_to?(method),  
obj.metaclass.respond_to?(method), obj.superclass.respond_to?(method)])
     elsif obj.nil?
       arr = [[nil.class.respond_to?(method), nil.metaclass.respond_to? 
(method), NoMethodError]]
     else
       arr = find_respond_to_in_class_heirarchy(obj.class, method)
       arr.unshift([obj.class.respond_to?(method),  
obj.metaclass.respond_to?(method), NoMethodError])
     end
     arr
   end
end

class Object
   include Debugs
   def metaclass
     class << self
       self
     end
   end
end

Wow this whole metaclass, class, object, module relationship is pretty  
mindbending...

Cheers,
-Adam