From: "Iñaki Baz Castillo" <ibc@...>
Date: 2009-12-20T04:53:01+09:00
Subject: Re: special cased?

El Sábado, 19 de Diciembre de 2009, David A. Black escribió:
> I think you mean shouldn't it just look up @a (not @@a) in the parent
> -- and the answer is no :-) A and B are different objects, and
> therefore do not share instance variables.

  class A
    @a = "hello"
    
    def self.say
      puts defined?(@a).inspect
    end
  end

  A.say
  => "instance-variable"
  nil

  class B < A ; end

  B.say
  nil
  nil


But as I already explained, the line '@a = "hello"' is just parsed by Ruby 
interpreter when loading class A.

When creating class B (which inherits from A) the Ruby parser doesn't read the 
whole class A definition again. Instead it already has in memory all the 
class/instance methods defined for class A so it wouldn't read '@a = "hello"' 
anymore.

And because of it, B class object doesn't know @a as its instance variable, it 
knows nothing about @a.

-- 
Iñaki Baz Castillo <ibc@aliax.net>