From: Brian Candler <B.Candler@...>
Date: 2003-05-01T06:29:42+09:00
Subject: Re: [OO interface design] Pass-by reference VS encapsulation ?

On Thu, May 01, 2003 at 05:37:46AM +0900, ahoward wrote:
> alternatively, you could implement a module which enfores RI for mutable
> methods and extend any contact added to an addresssbook with this module -
> contacts outside of an addressbook do not need RI after all.

That's a very cool idea. Since the RI methods are in the object's singleton
class, doing a '.dup' will give you a fresh object without the RI methods -
in otherwords it copies a contact which is 'bound' into the addressbook and
gives you another object which is 'free'.

I am not sure about allowing one contact object to be shared between two
addressbooks though. Any change to the contact would have to be 'agreed' by
both addressbooks, which sounds like a fairly complicated two-phase commit
to avoid getting into an inconsistent state.

In the end it may be simpler to take a copy and check it back into the
addressbook(s) after any changes have been made. Sort of like having a
'post-it note' onto which you scribble the details, and then write them back
after editing. It involves data copying but it's how things would work if
you were using a distributed system like DRuby anyway.

Regards,

Brian.