Where's the best place to dynamically add singleton method?

ruby-talk
1

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"
      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?

Just wondering.

Regards,
Iain

2

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

···

On Thu, Apr 28, 2011 at 3:58 PM, Iain Barnett <iainspeed@gmail.com> wrote:

--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

3

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

···

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"
     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?

Just wondering.

Regards,
Iain

4

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

···

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

5

I'm glad to hear that we could help you. Thank you for letting us know!

Kind regards

  robert

···

On 06.05.2011 22:15, Iain Barnett wrote:

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

--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/