From: zdennis <zdennis@...>
Date: 2006-04-08T02:49:32+09:00
Subject: Re: Simple Question About Deleting Instances

zdennis wrote:
> 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).

class A
end

# this creates an instance of your class, which is of class A
a = A.new

# this opens the instance of class A itself, which is of class Class
class A
  class << self
  end
end

Zach