From: zdennis <zdennis@...>
Date: 2006-04-08T02:45:23+09:00
Subject: Re: Simple Question About Deleting Instances

Nathan Olberding wrote:
> zdennis wrote:
>> You are creating an instance variable @b on your class A. The class A is
>> an instance of the class Class, so it to can have instance variables.
> 
> Not to be a whiner, but is there a reason we can't just do attr_accessor 
> :@@var? What you're saying is logical, but it seems like we're getting 
> from point A to point B via point F.

No. You just need to understand how classes and instances of a class work.

attr_* methods set instance variables and get/set methods on an instance
of a class. It does this using symbols.

  class A
    attr_accessor :b
  end

:b will point to instance variable @b, on an instance of A.

If you want to use attr_* to set class variables you need to work on the
instance of the class itself. That is why we do:

  class A
    class << self
      attr_accessor :class_var
    end
  end

Because "class << self" opens up the instance of class A. And :class_var
will map to a '@class_var' instance variable on your class itself (and
not on an instance of your class).

If you want further shortcuts check out the facets or traits libraries
on rubyforge. They may have what you are looking for, although I would
ask you to understand how ruby works first before trying to shortcut this.

Zach