From: Dan Doel <djd15@...>
Date: 2003-08-22T02:23:31+09:00
Subject: Re: Class variables - a surprising result

Gawnsoft wrote:

>A class-instance variable is one in which the scope is specific to a
>given (sub)class.
>
>Am I correct in dimly recalling that Ruby has support for
>class-instance variables?
>

You are correct.  If you search the ruby-talk archives you'll find a 
discussion almost the same as this
one.  Bottom line was that you have to do something like this:

class Foo
    def initialize
        class << Foo
            @class_instance_var = 'c'
        end
    end
   
    def test
        class << Foo
            puts @class_instance_var
        end
    end
end

class Bar < Foo
    def initialize
        class << Bar
            @class_instance_var = 55
        end
    end
   
    def inc
        class << Bar
            @class_instance_var += 1
        end
    end
   
    def test
        class << Bar
            puts @class_instance_var
        end
    end
end

foo1 = Foo.new
bar1 = Bar.new
bar2 = Bar.new

foo1.test
bar1.test
bar2.test

bar1.inc

bar1.test
bar2.test

This prints:

c
55
55
56
56