From: Lionel Thiry <lthiryidontwantspam@...>
Date: 2005-03-17T00:19:56+09:00
Subject: Re: [ruby2] will '@@' disapear in ruby2?

Csaba Henk wrote:
> On 2005-03-15, Lionel Thiry <lthiryidontwantspam@skynetnospam.be> wrote:
> 
>>>Anyway, the short answer as far as I know is "no" :-)
>>
>>Too bad! :)
> 
> 
> I do like having them. In fact, they are globals, wrapped in the
> namespace of a class/module. There are situations when you need such a
> beast, and it's better than an explicit global... and better than using a
> container as a constant (just because constans don't like being
> reassigned), that's really ugly.
There's still class instance variable.

class MyClass
  @a = "class instance value"

  attr_reader :a
  def initialize(value)
   @a = value
  end

  def a_of_the_class
   self.class.a
  end

  class << self
   attr_reader :a
  end
end

my_instance = MyClass.new("instance value")
puts my_instance.a # output: instance value
puts my_instance.a_of_the_class # output: class instance value

other_instance = MyClass.new("other instance value")
puts other_instance.a # output: other instance value
puts other_instance.a_of_the_class # output: class instance value

I prefer that way of doing things over the @@ way.

> 
> My problem is that you can't really access them from the outside, unless
> accessor method are set up. By "from the outside" I mean that from code
> which is not in the scope of a "class/module Foo ... end" thingy. Does
> anyone know, eg, how to define a class variable in a nameless class?
With class instance variable, this is easier, I suppose, as you can write:
  class << self
   attr_reader :a
  end

--
Lionel Thiry