From: Joel VanderWerf <vjoel@...>
Date: 2008-04-12T15:06:45+09:00
Subject: Re: How to duplicate a object changing the class without attributes memory copy

I単aki Baz Castillo wrote:
> Hi, I'm doing a server and want to avoid memory innecesary operations.
> I have an array of headers:
>   headers_array
> 
> Each header is an object of "Header" class:
> 
> 	class Header
> 		attr_accessor :name, :body
> 		def initialize(name, body)
> 			@name = name
> 			@body = body
> 		end
> 	end
> 
> 
> There are also others specific headers soons of "Header" class:
> 
> 	class From < Header
> 		attr_accessor :uri
> 	end
> 
> 
> At the beggining "headers_array" just contain "Header" objects but
> after inspection I want to replace the header with @name='From' with a
> "From" object but since "name" and "body" attributes are the same I
> don't want a memory copy operation to allocate space for new object.
> 
> This is: I just want to change the Class of a "Header" object to
> "From" class, keeping the attributes without memory copy operation, is
> there any way? I imagine in C I'd do it by using pointers.

Why do you need a From class that is distinct from Header? Depending on 
the reason, it might work to make From a module:

module From
   # special From methods here
end

headers.each do |h|
   if h.name == "From"
     h.extend From
   end
   # or maybe something like:
   # h.extend const_get(h.name)
end

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407