From: Trevoke <trevoke@...>
Date: 2009-07-23T04:15:15+09:00
Subject: Re: Instantiating classes / sharing data between classes

On Jul 22, 1:26 pm, Gary Wright <gwtm...@mac.com> wrote:
> On Jul 22, 2009, at 12:11 PM, Chris Rhoden wrote:
>
> > class Doctor
> >  def modalities
> >    @@modalities ||= your stuff
> >  end
> > end
>
> I think reaching for class variables is almost always a mistake.
> Some alternatives that I would consider first:
>
> a) Use a constant:
>
> class Doctor
>    Modalities = query_for_modalities
> end
>
> b) Use a class method and lazy load the data
>
> class Doctor
>    def self.modalities
>       @modalities ||= query_for_modalities
>    end
> end
>
> I don't recommend class variables because their actual scope
> is very non-intuitive (class hierarchy scope, not class scope)
> and they add to the semantic load of a design when plain
> old instance variables (on the class object) will do just fine.
>
> Gary Wright

Gary -- these values ARE the same for EVERY SINGLE INSTANCE of the
class, and are not meant to be changed.
In this particular instance, are class variables fulfilling their
destiny?