From: John Wilger <johnwilger@...>
Date: 2006-10-28T03:44:18+09:00
Subject: Re: can there be a "with" construction?

On 10/27/06, matt neuburg <matt@tidbits.com> wrote:
> Some languages have a "with" construction, where undefined methods are
> routed to a designated object. Here's an example from UserTalk:
>
> with system.startup {
>    string(license)
> }
>
> UserTalk knows what "string" is, but when it can't find "license" it
> reinterprets it as system.startup.license, which works. In UserTalk, you
> can even chain these tests:
>
> with system.temp, system.startup {
>    string(license)
> }
>

Off the top of my head, you could do:

    $with_receivers = []

    def with( *receivers )
      prev_receivers = $with_receivers
      $with_receivers = receivers
      begin
        yield if block_given?
      ensure
        $with_receivers = prev_receivers
      end
    end

    def method_missing( meth, *args )
      receiver = $with_receivers.detect do |r|
        r.respond_to? meth
      end
      if receiver
        return receiver.send( meth, *args )
      else
        super
      end
    end

There's definitely some nastiness there with the global variable, and
I'm sure someone is going to point out where this completely falls
apart within minutes of me posting it -- but it works for simple
cases, at least.

-- 
Regards,
John Wilger
http://johnwilger.com

-----------
Alice came to a fork in the road. "Which road do I take?" she asked.
"Where do you want to go?" responded the Cheshire cat.
"I don't know," Alice answered.
"Then," said the cat, "it doesn't matter."
- Lewis Carrol, Alice in Wonderland