def subscribe(self, listener, init=False):
"""
Register a callback function to be called when the VigilantAttributeBase
is changed
listener (function): callback function which takes as argument val the
new value
init (boolean): if True calls the listener directly, to initialise it
"""
assert callable(listener)
if isinstance(listener, types.BuiltinMethodType):
self._listeners.add(listener)
else:
self._listeners.add(WeakMethod(listener))
if init:
listener(self.value)
def subscribe(self, listener, init=False, **kwargs):
"""
Register a callback function to be called when the VigilantAttributeBase
is changed
listener (function): callback function which takes as argument val the
new value
init (boolean): if True calls the listener directly, to initialise it
Additional keyword arguments can be provided. They will be passed to
listener *ONLY ONCE* and only if `init` is True!
One of the reasons for this, is that we cannot easily store the `kwargs`
into the `_listeners` set, because `dicts` are not hashable.
"""
assert callable(listener)
self._listeners.add(WeakMethod(listener))
if init:
listener(self.value, **kwargs)
def __init__(self, notifier, uri, max_discard, zmq_ctx):
"""
notifier (callable): method to call when a new value arrives
uri (string): unique string to identify the connection
max_discard (int)
zmq_ctx (0MQ context): available 0MQ context to use
"""
threading.Thread.__init__(self, name="zmq for VA " + uri)
self.daemon = True
self.uri = uri
self.max_discard = max_discard
self._ctx = zmq_ctx
# don't keep strong reference to notifier so that it can be garbage
# collected normally and it will let us know then that we can stop
self.w_notifier = WeakMethod(notifier)
# create a zmq synchronised channel to receive commands
self._commands = zmq_ctx.socket(zmq.PAIR)
self._commands.connect("inproc://" + uri)
# create a zmq subscription to receive the data
self.data = zmq_ctx.socket(zmq.SUB)
self.data.connect("ipc://" + uri)
def unsubscribe(self, listener):
self._listeners.discard(WeakMethod(listener))