From: "Iñaki Baz Castillo" <ibc@...>
Date: 2009-03-31T07:05:58+09:00
Subject: Re: When to use instance variables @

El Martes 31 Marzo 2009, Albert Schlef escribió:
> In Ruby you declare nothing. (That's unlike languages like Java, C,
> etc., where everything has to be declated before use.)

This is not true when using class variables (@@). These need to be "declared" 
at the beginning of the class:


class KK

    @@koko   # <-- WRONG since no assignement is done.
             #     @@koko = #SOMETHING#   is required.

    def show_var
      puts "koko = #{@@koko}"
    end

    def set_var(v)
      @@koko = v
    end

end


irb(main):022:0> k=KK.new

irb(main):023:0> k.show_var
NameError: uninitialized class variable @@koko in KK

irb(main):024:0> k.set 123
irb(main):025:0> k.show_var
koko = 123


-- 
Iñaki Baz Castillo <ibc@aliax.net>