From: dblack@...
Date: 2003-10-13T05:23:46+09:00
Subject: Re: Newbie Class variable question

Hi --

On Mon, 13 Oct 2003, Elias Athanasopoulos wrote:

> This sounds a little bit wierd to me, since, in the book[*] I have,
> the author accesses a class variable implicitly, without having
> define self.foo and foo inside the class.

Class variables are directly visible only down the class hierarchy:

  class A
    @@x = 1
  end

  class B < A
    puts @@x      # 1
  end

You can give access to them, but you have to do it explicity:

  class A
    def self.peek   # technically you don't have to call it info :-)
      @@info
    end
    def self.poke(x)
      @@info = x
    end
  end

(This is similar to the kind of get/set methods that are often
implemented using instance variables, but the resemblance is
superficial.  Class variables are a different creature, and therfore
not a drop-in replacement for instance variables.)

Just to try to get it all clear: do you have a page number in The Ruby
Way for the example you mentioned?


David

-- 
David Alan Black
home: dblack@superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav