From: Mark Hubbart <discordantus@...>
Date: 2005-01-20T05:11:46+09:00
Subject: Re: value by reference

On Thu, 20 Jan 2005 04:16:02 +0900, Florian Gross <flgr@ccan.de> wrote:
> Mark Hubbart wrote:
> 
> > when you call Ref.new(obj), you get back a Ref object, which will
> > appear in every way to be the "obj" that you passed to Ref.new. It
> > will give the same id, behave the same, respond to the same methods,
> > etc.
> >
> > Only two differences (that I see):
> > First, it responds to two extra methods: __value__ and become. become
> > replaces the object that is being referenced, and returns the old
> > value. __value__ returns the object being referenced, without the Ref
> > wrapper. You should use this method any time you want to serialize or
> > Marshal the value.
> > Second, it circumvents the public/private method checks, so you can
> > call private methods directly on the reference. Sorry. Don't have the
> > time to figure out how to fix that without eval.
> 
> Third:
> 
> Ref.new(false) or Ref.new(nil) do not act like you would expect them to
> in conditional contexts:
> 
> do_something if ref # always done
> x = ref || y # x is always ref

Ah, I hadn't thought of that. I guess if you would need to
de-reference in conditionals:
  do_something if ref.__value__

> Fourth:
> 
> Some of Ruby's C methods want their arguments to be instances of a
> particular class. They won't even call the usual #to_x methods.
> str.scan(ref) is one example of that.

I didn't know of that one. So String.scan doesn't use duck typing?

> Fifth:
> 
> Object.instance_method(:inspect).bind(ref).call calls the #inspect
> method of the ref, not of the Object it refers to.

I would consider that a feature :) at a later time, a method could be
added, __ref__, would would allow you to call normal ruby methods on
the reference object; get its id, inspect it, etc.

This was really just a proof-of-concept... and you showed a couple of
big holes in it. :) Ahh, well. I suspect that for most things, this
will work, with stated caveats.

cheers,
Mark