[PEAK] Using peak.model as an observer subject
quale1 at charter.net
Wed Sep 1 22:11:12 EDT 2004
"Phillip J. Eby" <pje at telecommunity.com> writes:
> Looks pretty good to me. Personally, I'd use peak.events "event
> source" objects such as
> 'events.Broadcaster' instances rather than creating a new callback
> facility. This would eliminate the need for the _callbacks dictionary
> and a fair bit of logic; i.e. something like:
> class ObservableAttr(model.Attribute):
> newVerbs = [('get_event', '%(singularName)sEvent')]
> def get_event(feature, element):
> key = feature.attrName+'__event'
> return feature.__dict__[key]
> except KeyError:
> return feature.__dict__.setdefault(key,events.Broadcaster())
> def _onLink(feature, element, item, posn=None):
> Then, to subscribe to a feature, you'd do:
> Of course, this only calls 'callback' once; you'd probably use:
> source = anElement.someFeatureNameEvent()
> unsubscribe = events.subscribe(source, callback)
> which handles weak referencing for you, and automatically re-adds the
> callback each time the event fires.
Thanks. This is very nice. I'll use it.
I have a Python 101 type question: What is the advantage of using
key = feature.attrName+'__event' instead of key = '__event'?
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