def track_passive(self, oobkey, tracker, tracked, entityname, callback=None, mode="db", *args, **kwargs):
"""
Passively track changes to an object property,
attribute or non-db-attribute. Uses cache hooks to
do this on demand, without active tracking.
tracker - object who is tracking
tracked - object being tracked
entityname - field/property/attribute/ndb nam to watch
function - function object to call when entity update. When entitye <key>
is updated, this function will be called with called
with function(obj, entityname, new_value, *args, **kwargs)
*args - additional, optional arguments to send to function
mode (keyword) - the type of entity to track. One of
"property", "db", "ndb" or "custom" ("property" includes both
changes to database fields and cached on-model properties)
**kwargs - additional, optionak keywords to send to function
Only entities that are being -cached- can be tracked. For custom
on-typeclass properties, a custom hook needs to be created, calling
the update() function in this module whenever the tracked entity changes.
"""
# always store database object (in case typeclass changes along the way)
try: tracker = tracker.dbobj
except AttributeError: pass
try: tracked = tracked.dbobj
except AttributeError: pass
def default_callback(tracker, tracked, entityname, new_val, *args, **kwargs):
"Callback used if no function is supplied"
pass
thid = hashid(tracked)
if not thid:
return
oob_call = (function, oobkey, tracker, tracked, entityname, args, kwargs)
if thid not in self.track_passive_subs:
if mode in ("db", "ndb", "custom"):
caches.register_oob_update_hook(tracked, entityname, mode=mode)
elif mode == "property":
# track property/field. We must first determine which cache to use.
if hasattr(tracked, 'db_%s' % entityname.lstrip("db_")):
hid = caches.register_oob_update_hook(tracked, entityname, mode="field")
else:
hid = caches.register_oob_update_hook(tracked, entityname, mode="property")
if not self.track_pass_subs[hid][entityname]:
self.track_pass_subs[hid][entityname] = {tracker:oob_call}
else:
self.track_passive_subs[hid][entityname][tracker] = oob_call
def untrack_passive(self, tracker, tracked, entityname, mode="db"):
"""
Remove passive tracking from an object's entity.
mode - one of "property", "db", "ndb" or "custom"
"""
try: tracked = tracked.dbobj
except AttributeError: pass
thid = hashid(tracked)
if not thid:
return
if len(self.track_passive_subs[thid][entityname]) == 1:
if mode in ("db", "ndb", "custom"):
caches.unregister_oob_update_hook(tracked, entityname, mode=mode)
elif mode == "property":
if hasattr(, 'db_%s' % entityname.lstrip("db_")):
caches.unregister_oob_update_hook(tracked, entityname, mode="field")
else:
caches.unregister_oob_update_hook(tracked, entityname, mode="property")
try: del self.track_passive_subs[thid][entityname][tracker]
except (KeyError, TypeError): pass