From: Jacob Fugal <lukfugl@...>
Date: 2006-10-28T03:06:33+09:00
Subject: Re: can there be a "with" construction?

On 10/27/06, Gennady Bystritsky <Gennady.Bystritsky@quest.com> wrote:
> matt neuburg 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)
> > }
> >
> > That means we try system.temp.license and if that doesn't exist we
> > proceed to system.startup.license.
> >
> > So my question is: is Ruby amenable to this kind of construction? Is
> > there a way to bend the language to that it acts like this? Thx - m.
>
> Something like this?
>
> def with(*objects)
>   begin
>     yield
>   rescue NoMethodError => exception
>     o = objects.detect { |_o|
>       _o.respond_to? exception.name
>     } or raise
>
>     o.send exception.name, *exception.args
>   end
> end

It's a start, but:

1) I don't think we really want to redispatch NoMethodErrors for
messages that had an explicit receiver. Only the ones with implicit
receivers.

2) it stops execution of the block after redispatching the first exception:

  with(Time) do
    "aaa".now
    puts "Never get here"
  end # nothing printed

Jacob Fugal