From: "David A. Black" <dblack@...>
Date: 2003-12-10T03:04:16+09:00
Subject: Re: Inheriting variables, super, and "not super"?

Hi --

On Wed, 10 Dec 2003, Hugh Sasse Staff Elec Eng wrote:

> Is there a way in a method to say
> "ignore this if called as super"?
> 
> I am trying to inherit variables from a superclass, but I may need
> them different in the subclass, so I can't use class variables.

Might you make use of instance variables of the classes themselves?
That might be a cleaner way to preserve state on a per-Class basis.
(I don't know whether it fits in with the whole picture though.)

> Instance variables are not passed on to subclasses, so to initialize
> them I need to call super within initialize...
> 
> Also, at present, some of my initialization code sets up other
> things which make sense for an instance of that class, but not when
> I'm using an instance of a subclass.
> 
> Is there an idiom like
> 
> class Y < Z
>   def initialize()
>     @y_var = 0
>     if self.class == Y
>       y_init
>     end
>   end
> end
> 
> 
> class X < Y
>   def initialize
>     super
>     @x_var = 0
>   end
> end
> 
> Or does this show I doing something horribly wrong?

I have a feeling that if you're looking at two classes whose objects
have such different needs, it may be that the case for having one of
them be a subclass of the other is not all that strong.  

Do you think a module-centered design would work better?  You could
un-verticalize (?) the structure, and bring in what each class or even
each object needs.


David

-- 
David A. Black
dblack@wobblini.net