From: David Vallner <david@...>
Date: 2006-02-21T11:35:38+09:00
Subject: Re: Class variables and Constants

Dňa Pondelok 20 Február 2006 14:50 dblack@wobblini.net napísal:
> > AAAAAAAHHHHHHHHH!!!!!!!!!!!!
> > I've been playing with this the whole night. I am not gonna stop until
> > I've finished writing a clear document that explains absolutely
> > everything.
>

I tried to do Poor Man's Traits in Java using static fields. I feel your pain.

It's especially likely to cause initialization timing bugs - when I loaded the 
page from the webapp after a server restart, everything worked fine - by some 
strange coinkydink, the classes loaded earlier weren't used after they got 
clobbered by the subclasses loaded earlier. Lossage ensued after a page 
reload.

> I think Matz is planning to change class variables in 2.0 so that they
> are class/module scoped rather than hierarchy scoped.  Meanwhile,
> here's another fun variant:
>
> class A
> end
>
> class B < A
>    @@var = 10
>    def self.var
>      @@var
>    end
> end
>
> class A
>    @@var = 20
>    def self.var
>      @@var
>    end
> end
>
> p A.var
> p B.var
>

Oh dear. I do hope the change gets into 2.0, I can't wait for Java trolls to 
ramble against it...

(Now don't tell anyone, but I have a hunch class instance variables actually 
work like you'd expect in this case. I think.)

David Vallner