From: dblack@...
Date: 2006-10-11T22:08:25+09:00
Subject: Re: Singleton classes and Singleton pattern

Hi --

On Wed, 11 Oct 2006, Wilhelm wrote:

> I just happened upon singleton classes, and was wondering two things:
>
> 1) There's no difference between these two codes, right?  Is there an
> advantage or disadvantage over either?  Does Ruby put bar() into the
> same virtual class object for both?
>
> class Foo
>  class << self
>    def bar
>    end
>  end
> end
>
> class Foo
>  def self.bar
>  end
> end

See the thread from a couple of days ago called '"def self.method" vs
"class << self; def method"'.

> 2) A singleton class has nothing to do with the singleton design
> pattern, right?  They only share the same name because there is only
> ever one of them.

That's correct.  The predicate "singleton" applies to both, but
they're not the same as each other.


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org