From: Robert Dober <robert.dober@...>
Date: 2008-07-26T02:11:00+09:00
Subject: Re: simple module for "count my instances" behaviour

On Fri, Jul 25, 2008 at 6:40 PM, ara.t.howard <ara.t.howard@gmail.com> wrote:
>
> On Jul 25, 2008, at 7:22 AM, Julien Thewys wrote:
>
>> I meant other than for hacking purpose.
>
>
>
> there are many good reasons - one is for subclassing, if you override new
> clients do not have to remember to call 'super'
>
> class C
>  def C.new *a, &b
>    (object = allocate).instance_eval do
>      init *a, &b
>      initialize *a, &b
>      self
>    end
>  end
>
>  def init
>    @you = 'do not have to remember to call this'
>  end
> end
>
>
> class D < C
>  def initialize
>  end
> end
>
>
> another reason is for instance in the case of dike.rb, by re-defining 'new'
> it can track object creation, register a finalizer, and thereby track the
> object lifecycle to detect memory leaks
>
> regards.
>
> a @ http://codeforpeople.com/
> --
> we can deny everything, except that we have the possibility of being better.
> simply reflect on that.
> h.h. the 14th dalai lama
>
>
>
>
>
Ara I know your code is quite fine and demonstrating what you wanted
to, I am however still not sure that
I brought my point across :(

The dilemma of a way to redefine new statically (1) or dynamically (2)
is to allow it to tolerate other new implementations in the
inheritance chain.

(1)
class C
   def self.new *args, &blk
      super(*args, &blk).instance_eval do
         ...
         self
      end
    end
end

(2)

module M
  def self.inherited a_mod
      return if Class === a_mod
      class << a_mod
          alias_method :__old__, :new rescue nil
          self
      end.module_eval do
          def new *args, &blk
             __old__(*args,&blk).instance_eval do
               ...
               self
          end*

Cheers
Robert


-- 
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There's no one thing that's true. It's all true.
--
Ernest Hemingway