Class-based event handlers

A light-weight event-handler framework based on event classes is provided by the zope.event.classhandler module.

Handlers are registered for event classes:

>>> import zope.event.classhandler

>>> class MyEvent(object):
...     def __repr__(self):
...         return self.__class__.__name__

>>> def handler1(event):
...     print("handler1 %r" % event)

>>> zope.event.classhandler.handler(MyEvent, handler1)

Descriptor syntax:

>>> @zope.event.classhandler.handler(MyEvent)
... def handler2(event):
...     print("handler2 %r" % event)

>>> class MySubEvent(MyEvent):
...     pass

>>> @zope.event.classhandler.handler(MySubEvent)
... def handler3(event):
...     print("handler3 %r" % event)

Subscribers are called in class method-resolution order, so only new-style event classes are supported, and then by order of registry.

>>> import zope.event
>>> zope.event.notify(MySubEvent())
handler3 MySubEvent
handler1 MySubEvent
handler2 MySubEvent