From: Joel VanderWerf <vjoel@...>
Date: 2002-02-12T04:19:06+09:00
Subject: Re: Class variable madness

Yukihiro Matsumoto wrote:
...
> That's what class variables are.  Class variables are variables to be
> shared among class hierarchy.  They are not only shared by instance of
> the class, but also shared by instances of subclasses.  As a result,
> you cannot define class variables of same names in subclass.
> 
>                                                         matz.

...unless you define it in the subclass *first*, right?

irb(main):001:0> class A; end
nil
irb(main):002:0> class B<A; @@x=0; end
0
irb(main):003:0> class A; @@x=1; end
1
irb(main):004:0> class B; @@x; end
0
irb(main):005:0> class A; @@x; end
1

So the semantics depends on the order of definition. Because of this
behavior, I treat class vars sort of like globals and use them only in
prototype code, quick and dirty code, etc. For code that I can think
about more (and expend more keystrokes), I use class instance variables,
and write a bunch of accessors.

--
Joel VanderWerf                          California PATH, UC Berkeley
mailto:vjoel@path.berkeley.edu                     Ph. (510) 231-9446
http://www.path.berkeley.edu                       FAX (510) 231-9512