[Zope3-dev] Event service should adapt to ISubscriber

[Steve Alexander]

I'm working on a Zope 3 project.

I want to keep my implementation classes pretty free of zope3-isms. I 
have my interfaces in package/intefaces.py, my implementation classes in 
package/system.py, and I've encapsulated all zope3-isms into adapters in 
package/adapters.py.

One class needs its instances to clear certain indexes when something 
not directly related to it changes.

The clear way to do this is to use the Zope3 event service.

I need to get the instance hooked up to the event service after being 
added, and unhooked from it on being removed. That's easily sorted with 
an adapter:

class FooSystemSubscriptionAdapter:
     __implements__ = IAddNotifiable, IDeleteNotifiable

     def __init__(self, foo_system)
         self.context = foo_system

     def manage_afterAdd(self):
         'See IAddNotifiable'
         es = getService(self.context, 'Subscriptions')
         es.subscribe(self.context, IFooEvent)

     def manage_afterDelete(self):
         'See IDeleteNotifiable'
         es = getService(self.context, 'Subscriptions')
         es.subscribe(self.context, IFooEvent)

I can register this adapter using zcml.

However, I still need to make the implementation class implement 
ISubscriber so that it can be validly subscribed to the event service, 
and can receive its events.

What I'd rather do is implement a specific method, like 
_notifyFooChanged() in my pythonic implementation class, and make an 
ISubscriber adapter for my class that will get notified of an IFooEvent, 
and call _notifyFooChanged() on its context.

     def notify(self, event):
         'See ISubscriber'
         if IFooEvent.isImplementBy(event):
             self.context._notifyFooChanged(event.fooDetails)


I'd also like to make ISubscribingAware something that can be adapted 
to, rather than the current situation where it has to be implemented by 
the object being subscribed to an event service.


Any objections to this?

--
Steve Alexander