From: Florian Gross <flgr@...>
Date: 2004-06-26T04:28:06+09:00
Subject: Re: Is it considered Harmful?

Jim Weirich wrote:

> Florian Gross said:
>> [problems with proxies]
> Comparisons are problematic because the first line of a comparison is
> often "Are you the same class as me?".  Proxies arent't the right class so
> the comparisons fail.

It depends -- the answer to that question can be overloaded in most 
cases. (Though Object.instance_method(:class).bind(obj).call will always 
give you the real class and I think that some of the internal methods 
actually do something like that.)

> Actually, rather than a become or class= method, I would be interested in
> a swap_identitys method.  For example, to make a proxy object real ...
> 
>   def make_real
>     obj = read_real_object_from_the_database
>     swap_identities(self, obj)
>   end
> 
> When identities are swapped, every reference in the system to the first
> object will magically become a reference to the second object, and
> vice-versa.

This is how Squeak implements this AFAIK -- it just iterates through all 
Object references and changes them.

I'm not sure, but this could be a bit slow, maybe. (And I'm not sure if 
it would be a general solution for the problems with Proxy objects -- it 
would work in the lazy database example, but there might be other 
problematic use cases.)

Regards,
Florian Gross