From: Sebastian <shfriedrich@...>
Date: 2007-01-25T10:05:10+09:00
Subject: Re: Class Variables and Singelton Mix-Ins

uuh-ooh. i guess i could use an instance variable for the Singleton 
class instead :)

>     def greeting
>       @greeting ||= self.determine_greeting
>     end

It seems to have the exact same effect than a class variable defined in 
the class. Is this correct?


On 2007-01-24 18:51:46 -0600, Sebastian <shfriedrich@gmail.com> said:

> I'm trying to find a way to declare class variables in a module that 
> can be mixed into class methods and retain scope for only that 
> particular class instead of being defacto module-variables.
> 
> Here's a simplified example (albeit somewhat silly) of what i'm trying to do:
> 
> module Foo
>   module Bar
>       #...some instance methods
> 
>     def self.included(klass)
>       klass.extend(BarClassMethods)
>     end
> 
>   end
> 
>   module BarClassMethods
> 
>     def greeting
>       @@greeting ||= self.determine_greeting
>     end
> 
>     def determine_greeting
>       hello
>     end
> 
>   end
> end
> 
> class A
>   include Foo::Bar
> 
>      def self.hello
>        "hello from A"
>      end
> 
> end
> 
> class B
>   include Foo::Bar
> 
>   def self.hello
>      "hello from B"
>    end
> 
> end
> 
> puts A.greeting
> #=> 'hello from A'
> 
> puts B.greeting
> #=> 'hello from A'
> 
> The result i would hope for is "hello from A" and "hello from B" 
> respectively. But since @@greeting is really scoped module-wide it is 
> only intialized once. How can i force the class variable to pertain 
> only to the singelton class that mixes it in?