From: "David A. Black" <dblack@...>
Date: 2008-06-09T15:05:15+09:00
Subject: Re: Singleton object vs. enhancing singleton class

Hi --

On Mon, 9 Jun 2008, Paul McMahon wrote:

> In ruby, as class are singleton objects, does anyone have any ideas when

I'd just say: classes are objects. Like other objects, they can have
methods added to them on a per-object basis (give or take the fact
that "per-object" in the case of a class actually includes
subclasses).

> a a singleton object should be used vs. simply adding methods to the
> class?  For example,
>
> class Foo
>  include Singleton
>  def bar
>  end
> end
>
> vs.
>
> class Foo
>  def self.bar
>  end
> end

I don't see these techniques as addressing the same problem or being
likely candidates to replace each other. I'd go by what you need. If
you need a class that has only one instance, then use Singleton. If
you've got a situation where there's class-level (as opposed to
instance-level) knowledge involved, then use a class method.


David

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