From: ara.t.howard@...
Date: 2006-07-11T23:41:40+09:00
Subject: Re: Object IDs

On Tue, 11 Jul 2006, Guillaume Marcais wrote:

>
> Le 11 juil. 06, � 10:10, Alex Young a �crit :
>
>> A couple of quick questions:
>> 
>> a) Are object id's ever reused within the life of a Ruby process?
>
> I believe that Object#equal? compares ids if not overridden.
>
>> 
>> b) Are object id's unique across the whole Ruby process, or only within a 
>> given context?
>
> Unique across the process.


if you wait long enough they can be recycled so i wouldn't say they are unique
'across' a process.  that is to say ruby code which does this

   hash = Hash.new{|h, object_id| h[object_id] << 42}

will stack info about two different objects if it runs long enough or is
simply unlucky and only runs for a short time.

in otherwords

   id = object.object_id

   # time

   value = ObjectSpace::_id2ref id


may or may not retreive the same object and the error may or may not go
unnoticed.

in summary, i'd say that object_ids are unique in a given context, that
context being an instant of time in a given process.  as time progresses, even
by a millisecond, the chances of objects being recycled increases.  fyi.


regards.

-a
-- 
suffering increases your inner strength.  also, the wishing for suffering
makes the suffering disappear.
- h.h. the 14th dali lama