From: Joel VanderWerf <vjoel@...>
Date: 2005-06-20T14:56:09+09:00
Subject: Re: Wrapped load

Patrick Hurley wrote:
> I am building an internal batch processor -- I am not worried about
> malicious code (rm -rf *) type stuff, but I would like to be able to
> run most any ruby code without worrying about side effects in the
> batch processor, so a wrapped load sounded perfect.
> 
> I wanted to isolate changes to existing classes, so I put together
> this ever useful program (foo.rb):
> 
> module Kernel
>   alias old_puts puts
> 
>   def puts(*args)
>     args.each do |stuff|
>       old_puts "Fancy #{stuff}"
>     end
>   end
> 
>   def boo(x)
>     puts x ** 2
>   end
> 
> end
> 
> puts "Wow"
> 
> 
> ------------------------------ and then this even more impressive test
> body ------
> puts "One"
> load('foo.rb', true)
> puts "Two"
> load('foo.rb', false)
> puts "Three"
> 
> -------------------------------------------------------------------------------------------------------
> Which outputs:
> 
> One
> Wow
> Two
> Fancy Wow
> Fancy Three
> 
> What I really wanted was:
> One
> Fancy Wow              (how do I get this?)
> Two
> Fancy Wow
> Fancy Three
> 
> As it stands the wrapped code does not execute the same -- is there a
> way to get it to, without having those effects leak into the loading
> application?
> 
> Thanks
> Patrick
> 

I think this goes beyond just wrapping the file in a module, as you 
found out. It sounds like you want every object created by the loaded 
file to have its #puts method replaced with the one you defined. That's 
starting to sound like David Alan Black's Behaviors concept:

http://www.wobblini.net/ruby/behaviors/

Maybe David can comment...?