From: dblack@...
Date: 2006-10-29T01:17:19+09:00
Subject: Re: Class attribute unique to subclasses but used in parent class

Hi --

On Sun, 29 Oct 2006, David Vallner wrote:

> lcor1979@gmail.com wrote:
>> What I'll like, is that Child1 and Child2 have their own values of
>> @@test, but @@test should be initialized and used in Parent.
>> Also, @@test cannot be an instance variable because it is heavy to
>> initialize and will be common to all instances of Child1 or Child2.
>>
>
> Class variables and class instance variables sound way too much like
> global state coming into the system through a backdoor, I'd avoid both.
>
> Personally, I'd replace lookup through a class variable or class
> instance variable with injecting the shared object into instances. The
> less shared state, the more flexibility you gain in being able to rewire
> your objects.

Instance variables don't involve shared state, though; they're
strictly per object (Class object or otherwise).


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org