From: dblack@...
Date: 2006-11-16T21:01:14+09:00
Subject: Re: newbie question about attr_reader

Hi --

On Thu, 16 Nov 2006, ravi rao wrote:

> Hi,
> Why cant i have an attribute reader for a class variable.

Class variables are shared among many objects (the class, its
subclasses, all instances of all those classes), so they're not really
the right choice for representing an "attribute", which is generally
understood to be a property of a particular object.

You can certain write wrapper get/set methods around class variables,
and even automate the process.  You can also give your classes their
own attributes; since classes are objects, they can have attributes
like other objects.  To do that, you need to call attr_* in the
context of the class's singleton class:

   class C
     class << self
       attr_accessor :x
     end
   end

Now, the class object C has an attribute "x":

   C.x = 1
   puts C.new.class.x   # 1

etc.


David

-- 
                   David A. Black | dblack@rubypal.com
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org