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from functools import partial
from django.db.models.utils import make_model_tuple
from django.dispatch import Signal
class_prepared = Signal(providing_args=["class"])
class ModelSignal(Signal):
"""
Signal subclass that allows the sender to be lazily specified as a string
of the `app_label.ModelName` form.
"""
def _lazy_method(self, method, apps, receiver, sender, **kwargs):
from django.db.models.options import Options
# This partial takes a single optional argument named "sender".
partial_method = partial(method, receiver, **kwargs)
if isinstance(sender, str):
apps = apps or Options.default_apps
apps.lazy_model_operation(partial_method, make_model_tuple(sender))
else:
return partial_method(sender)
def connect(self, receiver, sender=None, weak=True, dispatch_uid=None, apps=None):
self._lazy_method(
super().connect, apps, receiver, sender,
weak=weak, dispatch_uid=dispatch_uid,
)
def disconnect(self, receiver=None, sender=None, dispatch_uid=None, apps=None):
return self._lazy_method(
super().disconnect, apps, receiver, sender, dispatch_uid=dispatch_uid
)
pre_init = ModelSignal(providing_args=["instance", "args", "kwargs"], use_caching=True)
post_init = ModelSignal(providing_args=["instance"], use_caching=True)
pre_save = ModelSignal(providing_args=["instance", "raw", "using", "update_fields"],
use_caching=True)
post_save = ModelSignal(providing_args=["instance", "raw", "created", "using", "update_fields"], use_caching=True)
pre_delete = ModelSignal(providing_args=["instance", "using"], use_caching=True)
post_delete = ModelSignal(providing_args=["instance", "using"], use_caching=True)
m2m_changed = ModelSignal(
providing_args=["action", "instance", "reverse", "model", "pk_set", "using"],
use_caching=True,
)
pre_migrate = Signal(providing_args=["app_config", "verbosity", "interactive", "using", "apps", "plan"])
post_migrate = Signal(providing_args=["app_config", "verbosity", "interactive", "using", "apps", "plan"])