From: Robert Klemme <shortcutter@...>
Date: 2011-04-28T23:09:15+09:00
Subject: Re: where's the best place to dynamically add singleton method?

On Thu, Apr 28, 2011 at 3:58 PM, Iain Barnett <iainspeed@gmail.com> wrote:
> Hi,
>
> If I've got a simple bit of initialisation code
>
>    def initialize( blah )
>      @listener = Blah.new blah
>    end
>
> and I'd like to add a singleton method to instance (because I don't want to monkey patch the Blah library) where's the best place to do that? I know I could do:
>
>    def initialize( blah )
>      @listener = Blah.new blah
>      def @listener.my_mental_method
>        self.give_it_up! "quickly"

No self needed here.

>      end
>    end
>
> but is this a good place to do it, or is there something more eloquent/perfomant? I'd like all instances, wherever they are created, to have this method, so is there a better way altogether?

First of all, I'd place the method in a module so you have less
definitions around.  Then I'd extend all instances with that module.
That also makes for easy addition of more methods.

module BlahExt
  def your_mental_method
    give_it_up! 'rather sooner than later'
  end
end

The automatic part could be handled by changing Bar's #new:

class <<Blah
  alias _new new

  def new(*a,&b)
    _new(*a,&b).extend BlahExt
  end
end

Note that this does not deal with inheritance nicely.  For that you
could do something similar with Bar's #initialize instead of #new.

If you do not need a global automatic I'd simply stick with

   def initialize( blah )
     @listener = Blah.new(blah).extend BlahExt
   end

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
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