From: Ross Bamford <rosco@...>
Date: 2005-11-27T01:02:28+09:00
Subject: Re: Nubish questions about syntax and gems

On Sat, 26 Nov 2005 15:24:36 -0000, David A. Black <dblack@wobblini.net>  
wrote:

> There's a simple way to get a handle on instance variables:
>
> At every moment during runtime, there is a current or default object
> -- "self".  Every time you see:
>
>    @var
>
> you are seeing an instance variable that belongs to "self", the
> current object.  There's never any ambiguity.
>
> "self", in turn, can be any object, including a Class object.  So,
> when in doubt, ask what "self" is:
>
>    class C
>      puts "In class definition body scope"
>      puts self                             # C (the class object)
>      @var = 1
>      puts @var                             # 1
>
>      def some_method
>        puts "In instance method scope"
>        puts self                       # an instance of C
>        puts @var                       # nil
>      end
>    end
>
>    c = C.new
>    c.some_method
>
> As you'll see from the output, the fact that the object C (the Class
> object) assigns to its instance variable @var does not affect the @var
> of an *instance* of C (which is uninitialized and therefore nil).
>
> You can think of class objects as wearing two hats: the "special case"
> hat of being an object factory, and the "civilian" hat of just being
> an object.  It's in "civilian" mode that class objects possess
> instance variables of their own, on the same footing as all other
> objects.
>

David,

That's a good explanation, thanks for that :) So I guess it makes sense  
that I can't access, say @var, in the class as @@var in instance methods.  
I think I was adding extra confusion for myself with that assumption.

Theres a lot of scope in these nuances, my mind is starting to work  
overtime ;)

Thanks again!

-- 
Ross Bamford - rosco@roscopeco.remove.co.uk