[Zope3-dev] event service.

[Chris McDonough]

Ah, good point. ;-)

----- Original Message -----
From: "Gary Poster" <garyposter@earthlink.net>
To: "Chris McDonough" <chrism@zope.com>; <zope3-dev@zope.org>
Sent: Wednesday, May 22, 2002 10:51 AM
Subject: RE: [Zope3-dev] event service.


> My take on this is that the event_type limits the events that will be
> processed by the filter: therefore, the filter *can* rely on receiving an
> event implementing the given event_type.  If you're building a filter for
an
> IObjectAddedEvent event_type, you can rely on the functions offered by the
> IObjectAddedEvent (getURL or whatever it is) being there.
>
> Gary
>
> -----Original Message-----
> From: zope3-dev-admin@zope.org [mailto:zope3-dev-admin@zope.org]On
> Behalf Of Chris McDonough
>
> I've backported the Zope 3 event service to Zope 2, and I've got an
> architecture question for those who might be willing to ponder it..
>
> The IEvent interface specifies a that Event objects must have a __call__
> method, but specifies no other features.
>
> Objects that implement the ISubscribable interface accept three arguments
to
> their "subscribe" method: subscriber, event_type, and filter.
>
> The Event Service implementation (which implements the ISubscribable
> interface)  runs the event through the filter method for each subscriber
> subscribed to a received event type.
>
> However, there is no interface-specified metadata on objects which
implement
> IEvent that would allow the filter method to switch on an attribute or
> method call value.  Currently, when the filter method is called with an
> object that implements IEvent, it really can't reliably do much with the
> object except call it.
>
> I'm wondering if there should be another interface type, perhaps
> IFilterableEvent that specifies another method, 'getFilterData', the
return
> value of which the filter could examine to see if it's interesting to a
> particular subscriber.
>
> - C
>
>
>
>
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