Hello All,
I am comming back to python after being away for several years.
I would like to use weak refs in an observer pattern implementation.
The problme that I have seems to be that weakrefs can't manage functions.
------------------- from docs:
Not all objects can be weakly referenced; those objects which can
include class instances, functions written in Python (but not in C),
methods (both bound and unbound), sets, frozensets, file objects,
generators, type objects, DBcursor objects from the bsddb module,
sockets, arrays, deques, and regular expression pattern objects. Changed
in version 2.4: Added support for files, sockets, arrays, and patterns.
-------------------------------------------------------
Is there a technique that I can use to leverage weak references to I
don't have to unregister my observers?
Thanks
Mike
PS. here is the code that I have been working with (Note: I commendout
out the weak ref creation.
--------------------------------------------------------------------
import types
class Observable(obje ct):
def addObserver(sel f, observer, events=None):
if not hasattr(self, '_observers'):
#self._observer s = weakref.WeakKey Dictionary()
self._observers = {}
if observer is None:
return
if events is not None and type(events) not in (types.TupleTyp e,
types.ListType) :
events = (events,)
self._observers[observer] = events
def removeObserver( self, callable):
if not hasattr(self, '_observers'):
return
if self._observers .has_key(callab le):
del self._observers[callable]
##
# Notify all currently-registered Observers.
#
# This observer will be called if the event is one that the
# Observer is interested in, or if event is 'None'
#
# @param event The event to notify the Observers about. None
# means no specific event.
#
# *args - standard arguments - passed through to observer
# **kw - keyword arguments - passed through to observer
def notifyObservers (self, event=None, *args, **kw):
if not hasattr(self, '_observers'):
return
for cb, events in self._observers .items():
if events is None or event is None or event in events:
if cb is not None:
cb(self, event, *args, **kw)
I am comming back to python after being away for several years.
I would like to use weak refs in an observer pattern implementation.
The problme that I have seems to be that weakrefs can't manage functions.
------------------- from docs:
Not all objects can be weakly referenced; those objects which can
include class instances, functions written in Python (but not in C),
methods (both bound and unbound), sets, frozensets, file objects,
generators, type objects, DBcursor objects from the bsddb module,
sockets, arrays, deques, and regular expression pattern objects. Changed
in version 2.4: Added support for files, sockets, arrays, and patterns.
-------------------------------------------------------
Is there a technique that I can use to leverage weak references to I
don't have to unregister my observers?
Thanks
Mike
PS. here is the code that I have been working with (Note: I commendout
out the weak ref creation.
--------------------------------------------------------------------
import types
class Observable(obje ct):
def addObserver(sel f, observer, events=None):
if not hasattr(self, '_observers'):
#self._observer s = weakref.WeakKey Dictionary()
self._observers = {}
if observer is None:
return
if events is not None and type(events) not in (types.TupleTyp e,
types.ListType) :
events = (events,)
self._observers[observer] = events
def removeObserver( self, callable):
if not hasattr(self, '_observers'):
return
if self._observers .has_key(callab le):
del self._observers[callable]
##
# Notify all currently-registered Observers.
#
# This observer will be called if the event is one that the
# Observer is interested in, or if event is 'None'
#
# @param event The event to notify the Observers about. None
# means no specific event.
#
# *args - standard arguments - passed through to observer
# **kw - keyword arguments - passed through to observer
def notifyObservers (self, event=None, *args, **kw):
if not hasattr(self, '_observers'):
return
for cb, events in self._observers .items():
if events is None or event is None or event in events:
if cb is not None:
cb(self, event, *args, **kw)
Comment