def _set_one(self, obj, value, from_opposite=False) -> None:
if not (isinstance(value, self.type) or (value is None)):
raise AttributeError(
f"Value should be of type {self.type.__name__}, got a {type(value)} instead"
)
old = self._get(obj)
# do nothing if we are assigned our current value:
# Still do your thing, since undo handlers expect that.
if value is old:
return
if old:
self._del(obj, old, from_opposite=from_opposite, do_notify=False)
if value is not None:
setattr(obj, self._name, value)
try:
self._set_opposite(obj, value, from_opposite)
except Exception:
setattr(obj, self._name, old)
raise
self.handle(AssociationSet(obj, self, old, value))
def _del_one(self, obj, value, from_opposite=False, do_notify=True):
value = self._get_one(obj)
if value is None:
return
self._del_opposite(obj, value, from_opposite)
try:
delattr(obj, self._name)
except AttributeError:
pass
else:
if do_notify:
self.handle(AssociationSet(obj, self, value, None))