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List:       ruby-talk
Subject:    Re: Singleton Class or Module Functions?
From:       "trans.  (T. Onoma)" <transami () runbox ! com>
Date:       2004-10-21 17:47:28
Message-ID: 200410211344.52319.transami () runbox ! com
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On Thursday 21 October 2004 10:04 am, Gavin Kistner wrote:
| On Oct 20, 2004, at 4:16 PM, trans. (T. Onoma) wrote:
| >   module ThisInstance
| >     class << self
| >       def hello
| >         puts "Hello World!"
| >       end
| >     end
| >   end
|
| Thank you for this; I'm just starting my project, and I have 6
| 'major-feature' handlers which are all Singleton classes -- namespace
| and functional-separation wrappers for a bunch of methods. The above
| smells cleaner to me.

From the responses (thanks for those BTW!) I gather that using modules in this 
way is only good if there is no _state_ involved. As Brian points out there 
are thread safety issues otherwise. In other words this is good if it's just 
a bag of functions --a `toolbox` if you will.

But David has also pointed out that rather then use the a heavy Singleton 
class, the virtual class (also called singleton) is probably better.

  a = Object.new
  class << a
   def hello
      puts "Hellow World!
    end
  end

As long as you don't need to ask a.is_a?(SpecialThing) this is lighter weight 
solution. But I'm not sure right off how that plays into the initialization 
difference you raise. Have any notions on that?

Likewise Thanks,
T.


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