From: ara.t.howard@...
Date: 2006-05-11T14:55:49+09:00
Subject: Re: plz help with binding

On Thu, 11 May 2006, Sergey Volkov wrote:


> Now I'm trying to create instance-var-less storage:
> #
> class C
>    def self.arr_meth( sym )
>        arr = []
>        define_method sym.to_sym, lambda{ arr }
>    end
>    arr_meth :arm
> end
> ca = C.new; ca.arm << 10
> cb = C.new; cb.arm << 20
> p ca.arm #-> [10, 20]
> p cb.arm #-> [10, 20]
> p( ca.arm.eql?( cb.arm ) ) #-> true
> #
> Why ca.arm, cb.arm share same local variable?
> Is it bug or feature?

because, in effect, this is what you've done

   class C
     ARR = []
     def arm() lambda{ ARM } end
   end

there are a lot of ways to do this but you want something like:

   harp:~ > cat a.rb
   class C
     def self.arr_meth am = nil
       @arr_meths ||= []
       @arr_meths << am.to_s if am
       @arr_meths
     end
     arr_meth :arm
     def initialize
       klass = self.class
       singleton_klass = class << self; self; end
       klass.arr_meth.each do |m|
         singleton_klass.module_eval do
           arr = []
           define_method m, lambda{ arr }
         end
       end
     end
   end

   ca = C.new; ca.arm << 10
   cb = C.new; cb.arm << 20

   p ca.arm #-> [10]
   p cb.arm #-> [20]
   p( ca.arm.eql?( cb.arm ) ) #-> false


   harp:~ > ruby a.rb
   [10]
   [20]
   false


neat idea btw.

hth.

-a
-- 
be kind whenever possible... it is always possible.
- h.h. the 14th dali lama