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__doc__ = """
Dirt Simple Events
A Dispatcher (or a subclass of Dispatcher) stores event handlers that
are 'fired' simple event objects when interesting things happen.
Create a dispatcher:
>>> d = Dispatcher()
Now create a handler for the event and subscribe it to the dispatcher
to handle Event events. A handler is a simple function or method that
accepts the event as an argument:
>>> def handler1(event): print(repr(event))
>>> d.subscribe(Event, handler1) # doctest: +ELLIPSIS
<rdflib.events.Dispatcher object at ...>
Now dispatch a new event into the dispatcher, and see handler1 get
fired:
>>> d.dispatch(Event(foo='bar', data='yours', used_by='the event handlers'))
<rdflib.events.Event ['data', 'foo', 'used_by']>
"""
__all__ = ["Event", "Dispatcher"]
class Event:
"""
An event is a container for attributes. The source of an event
creates this object, or a subclass, gives it any kind of data that
the events handlers need to handle the event, and then calls
notify(event).
The target of an event registers a function to handle the event it
is interested with subscribe(). When a sources calls
notify(event), each subscriber to that event will be called in no
particular order.
"""
def __init__(self, **kw):
self.__dict__.update(kw)
def __repr__(self):
attrs = sorted(self.__dict__.keys())
return "<rdflib.events.Event %s>" % ([a for a in attrs],)
class Dispatcher:
"""
An object that can dispatch events to a privately managed group of
subscribers.
"""
_dispatch_map = None
def set_map(self, amap):
self._dispatch_map = amap
return self
def get_map(self):
return self._dispatch_map
def subscribe(self, event_type, handler):
"""Subscribe the given handler to an event_type. Handlers
are called in the order they are subscribed.
"""
if self._dispatch_map is None:
self.set_map({})
lst = self._dispatch_map.get(event_type, None)
if lst is None:
lst = [handler]
else:
lst.append(handler)
self._dispatch_map[event_type] = lst
return self
def dispatch(self, event):
"""Dispatch the given event to the subscribed handlers for
the event's type"""
if self._dispatch_map is not None:
lst = self._dispatch_map.get(type(event), None)
if lst is None:
raise ValueError("unknown event type: %s" % type(event))
for l_ in lst:
l_(event)
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