From: Erik Veenstra <erikveen@...>
Date: 2007-01-19T22:55:28+09:00
Subject: Re: Hash#open! / Hash#close!

What about this one? It uses my personal, small, generic
delegator.

There's at least one thing I don't like: Since it's a
delegator, operations on h2 directly affect h1. A pure
functional approach would be more appropriate: Going from h1 to
h2 results in a copy of the data. When un_delegate'ing, we
should once again copy the data. But that consumes a bit more
memory... ;]

(I'll work out the functional one and post it in a couple of
minutes...)

gegroet,
Erik V. - http://www.erikveen.dds.nl/

----------------------------------------------------------------

 module EV
   class Delegator
     def initialize(real_object)
       @real_object      = real_object
     end

     def method_missing(method_name, *args, &block)
       @real_object.__send__(method_name, *args, &block)
     end

     def self.delegate(*args, &block)
       res       = self.new(*args)
     end

     def self.un_delegate(delegator_object)
       delegator_object.instance_variable_get("@real_object")
     end

     def self.open(*args, &block)
       res       = delegate(*args)

       if block
         begin
           block.call(res)
         ensure
           res   = un_delegate(res)
         end
       end

       res
     end
   end
 end

 class HashWithMethods < EV::Delegator
   def method_missing(method_name, *args, &block)
     method_name = method_name.to_s

     if method_name =~ /=$/
       key       = method_name[0..-2]
       value     = args[0]

       @real_object[key] = value
     else
       key       = method_name

       @real_object[key]
     end
   end
 end

 if __FILE__ == $0
   h1    = {"a"=>111, "b"=>222}

   HashWithMethods.open(h1) do |h2|
     h2.b        = 22222
     h2.c        = 33333
   end

   p h1
 end

----------------------------------------------------------------