From: Iain Barnett <iainspeed@...>
Date: 2011-05-07T05:15:20+09:00
Subject: Re: where's the best place to dynamically add singleton method?


On 28 Apr 2011, at 15:09, Robert Klemme wrote:

> 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
> http://blog.rubybestpractices.com/
> 


On 28 Apr 2011, at 15:15, Kresimir Bojcic wrote:

> I think you can achieve functionality that you desire by using mixins,
> modules and include statement... like this
> 
> 
> module CoolMethods
>  def my_mental_method
>     ....
>  end
> end
> 
> class UnfortunateUserOfCoolMethod
> 
>   include CoolMethods
>   ....
> 
> end
> 
> Also if you need method on a class you can use extend intstead of
> include....
> 
> 
> Best Regards,
> 
> Kresimir Bojcic
> 
> www.kresimirbojcic.com


Thanks to you both for the input. Sorry I didn't reply sooner but was snowed under with other things and wanted to think about it and do a bit of research. I've been reading a lot more on what's going on with details of the Ruby inheritance model, all that stuff in the background that I was getting along with fine without till now (which I think is a testament to the language), and your answers helped. 

Due to this I refactored things quite significantly so I've ended up not using this directly, but I've gone further for it.

Much appreciated

Regards,
Iain