From: Robert Klemme <shortcutter@...>
Date: 2008-10-21T15:03:44+09:00
Subject: Re: instance counter

On 20.10.2008 23:20, Pit Capitain wrote:
> 2008/10/20 Robert Klemme <shortcutter@googlemail.com>:
>> Do you have an example which cannot be handled as easily by a class
>> instance variable?  I can't think of any ATM - which does not mean it
>> does not exist.
> 
> In one example I remember I had a class inheritance hierarchy and
> needed to keep some information in the base class. I wanted to access
> this information from the subclasses without having to know the exact
> ancestor where the information was stored. The easiest way to do that
> was using a class variable.
> 
> Of course it would also be possible to use class instance variables
> and accessor methods like Dave suggested, but I didn't want to write
> "BaseClass.accessor_method".

class Base
   class <<self
     attr_accessor :foo
   end

   def foo
     Base.foo
   end

   def foo=(x)
     Base.foo=x
   end
end

class A < Base
end

class B < Base
end

B.new.foo=123
puts A.new.foo

If you need that more frequently you can even put this into a module 
which takes care of the rest.  Or you define an instance method on 
Module which sets up this scenario.

Kind regards

	robert