From: James Edward Gray II <james@...>
Date: 2006-11-15T01:42:12+09:00
Subject: Re: Immediate, Immutable, Singleton etc

On Nov 14, 2006, at 10:26 AM, Ilan Berci wrote:

> Singleton: This is a gof pattern meanting that you can have exactly  
> one
> instance of an object.

This term is often used with Ruby in a different manner.  In Ruby a  
"singleton method" is a method added to an individual object:

 >> normal = (1..5).to_a
=> [1, 2, 3, 4, 5]
 >> special = normal.dup
=> [1, 2, 3, 4, 5]
 >> class << special
 >>   def shuffle!
 >>     replace(sort_by { rand })
 >>   end
 >> end
=> nil
 >> special.shuffle!
=> [5, 1, 4, 2, 3]
 >> normal.shuffle!
NoMethodError: undefined method `shuffle!' for [1, 2, 3, 4, 5]:Array
         from (irb):10

Ruby does also have an implementation of the GoF pattern though, in  
the singleton standard library.

James Edward Gray II