Part of twisted.words.xish.utility View Source View In Hierarchy
Known subclasses: twisted.words.xish.xmlstream.XmlStream
EventDispatcher allows observers to be registered for
certain events that are dispatched. There are two types of events: XPath
events and Named events.
Every dispatch is triggered by calling
with a data object and, for named events, the name of the event.
When an XPath type event is dispatched, the associated object is assumed
to be an
instance, which is matched against all registered XPath queries. For every
match, the respective observer will be called with the data object.
A named event will simply call each registered observer for that
particular event name, with the data object. Unlike XPath type events, the
data object is not restricted to
can be anything.
When registering observers, the event that is to be observed is
specified using an
instance or a string. In the latter case, the string can also contain the
string representation of an XPath expression. To distinguish these from
named events, each named event should start with a special prefix that is
self.prefix. It defaults to
Observers registered using
are persistent: after the observer has been triggered by a dispatch, it
remains registered for a possible next dispatch. If instead
was used to observe an event, the observer is removed from the list of
observers after the first observed event.
Observers can also be prioritized, by providing an optional
priority parameter to the
methods. Higher priority observers are then called before lower priority
Finally, observers can be unregistered by using
|Method||addOnetimeObserver||Register a one-time observer for an event.|
|Method||addObserver||Register an observer for an event.|
|Method||removeObserver||Remove callable as observer for an event.|
|Method||dispatch||Dispatch an event.|
but is only triggered at most once. See there for a description of the
Each observer will be registered with a certain priority. Higher priority observers get called before lower priority observers.
|Parameters||event||Name or XPath query for the event to be monitored. (type: |
|observerfn||Function to be called when the specified event has been triggered. This
callable takes one parameter: the data object that triggered the event.
When specified, the |
|priority||(Optional) priority of this observer in relation to other observer that
match the same event. Defaults to |
The observer callable is removed for all priority levels for the specified event.
|Parameters||event||Event for which the observer callable was registered. (type: |
|observerfn||Observer callable to be unregistered.|
None, an XPath type event is
obj is assumed to be an instance of
event holds the name of the named event being
triggered. In the latter case,
obj can be anything.
|Parameters||obj||The object to be dispatched.|
|event||Optional event name. (type: |