From 3e7d72c2ce450546071dc0df72a25c8a0a0c0e8b Mon Sep 17 00:00:00 2001
From: Paul McCarthy <pauld.mccarthy@gmail.com>
Date: Wed, 1 Jun 2016 18:27:38 +0100
Subject: [PATCH] The Notifier class now allows notifiers to be grouped by
'topic'.
---
fsl/utils/notifier.py | 109 +++++++++++++++++++++++++++++-------------
1 file changed, 77 insertions(+), 32 deletions(-)
diff --git a/fsl/utils/notifier.py b/fsl/utils/notifier.py
index b7c50f500..21f40b38f 100644
--- a/fsl/utils/notifier.py
+++ b/fsl/utils/notifier.py
@@ -19,11 +19,18 @@ import props
log = logging.getLogger(__name__)
+DEFAULT_TOPIC = 'default'
+"""Topic used when the caller does not specify one when registering,
+deregistering, or notifying listeners.
+"""
+
+
class Notifier(object):
"""The ``Notifier`` class is a mixin which provides simple notification
- capability. Listeners can be registered/deregistered via the
- :meth:`register` and :meth:`deregister` methods, and notified via
- the :meth:`notify` method.
+ capability. Listeners can be registered/deregistered to listen via the
+ :meth:`register` and :meth:`deregister` methods, and notified via the
+ :meth:`notify` method. Listeners can optionally listen on a specific
+ *topic*, or be notified for all topics.
.. note:: The ``Notifier`` class stores ``weakref`` references to
registered callback functions, using the :class:`WeakFunctionRef`
@@ -35,37 +42,53 @@ class Notifier(object):
instance.
"""
new = object.__new__(cls)
- new.__listeners = collections.OrderedDict()
+ new.__listeners = collections.defaultdict(collections.OrderedDict)
return new
- def register(self, name, callback):
+ def register(self, name, callback, topic=None):
"""Register a listener with this ``Notifier``.
:arg name: A unique name for the listener.
:arg callback: The function to call - must accept this ``Notifier``
instance as its sole argument.
+ :arg topic: Optional topic on which fto listen for notifications.
"""
+ if topic is None:
+ topic = DEFAULT_TOPIC
+
# We use a WeakFunctionRef so we can refer to
# both functions and class/instance methods
- self.__listeners[name] = props.WeakFunctionRef(callback)
+ self.__listeners[topic][name] = props.WeakFunctionRef(callback)
- log.debug('{}: Registered listener {} (function: {})'.format(
- type(self).__name__,
- name,
- getattr(callback, '__name__', '<callable>')))
+ log.debug('{}: Registered listener {} '
+ '[topic: {}] (function: {})'.format(
+ type(self).__name__,
+ name,
+ topic,
+ getattr(callback, '__name__', '<callable>')))
- def deregister(self, name):
+ def deregister(self, name, topic=None):
"""De-register a listener that has been previously registered with
this ``Notifier``.
- :arg name: Name of the listener to de-register.
+ :arg name: Name of the listener to de-register.
+ :arg topic: Topic on which the listener was registered.
"""
- callback = self.__listeners.pop(name, None)
+ if topic is None:
+ topic = DEFAULT_TOPIC
+
+ listeners = self.__listeners.get(topic, None)
+
+ # Silently absorb invalid topics
+ if listeners is None:
+ return
+
+ callback = listeners.pop(name, None)
# Silently absorb invalid names - the
# notify function may have removed gc'd
@@ -73,6 +96,10 @@ class Notifier(object):
# in the dictionary.
if callback is None:
return
+
+ # No more listeners for this topic
+ if len(listeners) == 0:
+ self.__listeners.pop(topic)
callback = callback.function()
@@ -81,17 +108,33 @@ class Notifier(object):
else:
cbName = '<deleted>'
- log.debug('{}: De-registered listener {} (function: {})'.format(
- type(self).__name__, name, cbName))
+ log.debug('{}: De-registered listener {} '
+ '[topic: {}] (function: {})'.format(
+ type(self).__name__,
+ name,
+ topic,
+ cbName))
def notify(self, *args, **kwargs):
"""Notify all registered listeners of this ``Notifier``.
- All arguments passed to this method are ignored.
+
+ :args notifier_topic: Must be passed as a keyword argument.
+ The topic on which to notify. Default
+ listeners are always notified, regardless
+ of the specified topic.
+
+ All other arguments passed to this method are ignored.
"""
+ topic = kwargs.get('notifier_topic', DEFAULT_TOPIC)
+ listeners = [self.__listeners[topic]]
- listeners = list(self.__listeners.items())
+ if topic != DEFAULT_TOPIC:
+ listeners.append(self.__listeners[DEFAULT_TOPIC])
+
+ if sum(map(len, listeners)) == 0:
+ return
if log.getEffectiveLevel() >= logging.DEBUG:
stack = inspect.stack()
@@ -100,22 +143,24 @@ class Notifier(object):
srcMod = '...{}'.format(frame[1][-20:])
srcLine = frame[2]
- log.debug('{}: Notifying {} listeners [{}:{}]'.format(
+ log.debug('{}: Notifying {} listeners (topic: {}) [{}:{}]'.format(
type(self).__name__,
- len(listeners),
+ sum(map(len, listeners)),
+ topic,
srcMod,
srcLine))
+
+ for ldict in listeners:
+ for name, callback in list(ldict.items()):
- for name, callback in listeners:
-
- callback = callback.function()
-
- # The callback, or the owner of the
- # callback function may have been
- # gc'd - remove it if this is the case.
- if callback is None:
- log.debug('Listener {} has been gc\'d - '
- 'removing from list'.format(name))
- self.__listeners.pop(name)
- else:
- callback(self)
+ callback = callback.function()
+
+ # The callback, or the owner of the
+ # callback function may have been
+ # gc'd - remove it if this is the case.
+ if callback is None:
+ log.debug('Listener {} has been gc\'d - '
+ 'removing from list'.format(name))
+ ldict.pop(name)
+ else:
+ callback(self)
--
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