[Zope3-dev] ObjectHub notes: removing objects

[Steve Alexander]

>> (2) it's not a direct
>> parallel to what I proposed to do for object added events.
> 
> Symetry is good.

Symmetry is good for symmetrical things. I think this case is somewhat 
lopsided, on account of the object being already registered when it is 
removed. We're not interested in all object removed events, only in 
those where the object is already registered with the Hub.
This is different than the case when an object is added, where we need 
to decide whether to register it or not.


> I think the ObjectHub should maintain it's own registry and not rely on 
> something external to do it.

The Hub needs to maintain its own registry of HubId<-->location.


> The ObjectHub receiving an IObjectRemoved should unregister the object 
> and let any subscribers know that it's gone.

Yes. However, subscribers may be interested in the fact that the object 
was not simply unregistered, but was deleted and therefore unregistered.

Again, this is different from the case when an object is added, as the 
object is not registered at the time it is added, and so the adding of 
the object leading to its registration is not a concern of the Hub or 
its regular HubEvent subscribers.

Of course, adding an object to a container that is registered could 
cause some sort of ObjectChanged event to be sent on behalf of the 
container.

--
Steve Alexander