From: gabriele renzi <surrender_it@...>
Date: 2005-04-21T23:24:31+09:00
Subject: Re: accessor for Class Variable

Leonardo Francalanci ha scritto:
> I know it's a stupid question, but I can't find the answer...
> 
> Isn't there another way to have an accessor for a class variable than a 
> "def"??? Something like "attr_reader"?
> 
> class Outing < ActiveRecord::Base
>     @@planingList = [ "YES", "NO", "YES/NO"]
>     
>   def Outing.wind_directionList
>       return @@wind_directions
>   end
> end
> 
> 
> If the answer is somewhere in the docs, please point me to it.

AFAIK there is not, I think you're supposed to access a class variable 
directly from instances and class methods, and to generally use a 
constant when possible, wich is visible from outside.
In general the use case for class attributes accessible from the outside 
is not that much (in my own experience).

Anyway you should be able to write them easily with something like 
(untested):

class Class
  def class_attr sym
   module_eval "def self.#{sym}() @@#{sym} end"
   module_eval "def self.#{sym}=(x) @@#{sym}=x end"
  end
end

class C
  class_attr :foo
end