Source code for zope.event.classhandler

"""Class-based event handlers

A light-weight event-handler framework based on event classes.

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

import zope.event

__all__ = [

registry = {}

[docs]def handler(event_class, handler_=None, _decorator=False): """ Define an event handler for a (new-style) class. This can be called with a class and a handler, or with just a class and the result used as a handler decorator. """ if handler_ is None: return lambda func: handler(event_class, func, True) if not registry: zope.event.subscribers.append(dispatch) if event_class not in registry: registry[event_class] = [handler_] else: registry[event_class].append(handler_) if _decorator: return handler
def dispatch(event): for event_class in event.__class__.__mro__: for handler in registry.get(event_class, ()): handler(event)