From: Jamey Cribbs <jcribbs@...>
Date: 2006-03-06T00:16:51+09:00
Subject: Re: Kirbybase Hacks NilClass

Trans wrote:

># :title: NullClass
>#
># NullClass is essentially NilClass but it differs in one
># important way. When a method is called against it that it
># deoesn't have, it will simply return null value rather then
># raise an error.
>
>class NullClass #< NilClass
>  class << self
>    def new
>      @null ||= NullClass.allocate
>    end
>  end
>  def inspect ; 'null' ; end
>  def nil?  ; true ; end
>  def null? ; true ; end
>  def [](key); nil; end
>  def method_missing(sym, *args)
>    return nil if sym.to_s[-1,1] == '?'
>    self
>  end
>end
>
>module Kernel
>  def null
>    NullClass.new
>  end
>end
>
>class Object
>  def null?
>    false
>  end
>end
>
>  
>
Thanks, Trans!  I really like this.  It makes sense to just create one 
null object, like nil does.

Jamey