From: Trans <transfire@...>
Date: 2005-09-23T00:26:39+09:00
Subject: Re: Instantiating a subclass of NilClass.


Robert Klemme wrote:
> Hm...  I guess NilClass in Java lingo would be a final class, i.e., no
> inheritance allowed.
>
> Btw, why do you want to do that?  I mean, you can create a class with
> nil-like behavior (apart from the boolean behavior I guess) without
> inheriting NilClass, can't you?

Yea, but the boolean behavior is important. I'm using it in a
OpenStruct like class, so that:

  o = OpenStructLike.new
  o.foo          #=> null
  o.foo.bar      #=> null

As it is:

  o.foo          #=> nil
  o.foo.bar      #=> ERROR

> require 'singleton'
>
>   class NullClass
>     include Singleton
>
>     def inspect ; 'null' ; end
>     def nil?() true end
>     def method_missing(*args) ; self ; end
>   end
>
>   module Kernel
>     def null
>       NullClass.instance
>     end
>   end

Thanks, unfortunately w/o the boolean behavior it won't work
transparently.

T.