From: Brian Candler <B.Candler@...>
Date: 2007-02-09T21:06:38+09:00
Subject: Re: What is really a class instance variable compare to a class variable ?

On Fri, Feb 09, 2007 at 07:48:37PM +0900, Ruby Admirer wrote:
>   => So, an object instance variable is shared/seen by the derived object instances.

My understanding is:

(1) An instance variable is only visible to that object. It doesn't matter
what "class" the object is. It's not visible by any other objects, either of
the same class or a different class.

(2) A class instance variable is an instance variable of an object which
happens to be a class (its an object whose class is "Class"). This is also
private to that object, i.e. to the class. A subclass is a different object,
so has its own class instance variables.

(3) Class variables, i.e. @@foo, are voodoo. But yes I believe they are
shared by groups of classes in the same ancestry somehow.

B.