From: dblack@...
Date: 2006-10-23T20:23:10+09:00
Subject: Re: newbie: class attribute accessors?

Hi --

On Mon, 23 Oct 2006, Diego Virasoro wrote:

>> Please explain. Use an example.
>
> From what I understood, for any instance variable, I can make ruby
> automatically produce the accessors. For example:
>
> class Dog
>   @name
>   @@NumberOfLegs = 4
>
>   attr_accessor :name
> end
>
> x = Animal.new
> ...
> puts x.name
>
>
> However, I would like to do something similar for class variables. So
> for example in the above example, for @@NumberOfLegs.
>
> Is this possible?

See Farrel's answer; you can write wrapper methods.  Note, however,
that these are not exactly "attributes".  Class variables are shared
among many different objects (all the classes in a hierarchy; all the
instances of all those classes), so they can't represent an attribute
in the normal/usual sense.

You can certainly give your class objects attributes.  Just call
attr_accessor in the object's singleton class:

   class Dog
     class << self
       attr_accessor :number_of_legs
     end
     self.number_of_legs = 4
   end

   puts Dog.number_of_legs  # => 4
   Dog.number_of_legs = 10  # well, maybe attr_reader is better :-)


David

-- 
                   David A. Black | dblack@wobblini.net
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