From: Gary Wright <gwtmp01@...>
Date: 2009-07-23T02:26:56+09:00
Subject: Re: Instantiating classes / sharing data between classes


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