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- from django.apps import apps
- from django.dispatch import Signal
- from django.utils import six
-
-
- 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 __init__(self, *args, **kwargs):
- super(ModelSignal, self).__init__(*args, **kwargs)
- self.unresolved_references = {}
- class_prepared.connect(self._resolve_references)
-
- def _resolve_references(self, sender, **kwargs):
- opts = sender._meta
- reference = (opts.app_label, opts.object_name)
- try:
- receivers = self.unresolved_references.pop(reference)
- except KeyError:
- pass
- else:
- for receiver, weak, dispatch_uid in receivers:
- super(ModelSignal, self).connect(
- receiver, sender=sender, weak=weak, dispatch_uid=dispatch_uid
- )
-
- def connect(self, receiver, sender=None, weak=True, dispatch_uid=None):
- if isinstance(sender, six.string_types):
- try:
- app_label, model_name = sender.split('.')
- except ValueError:
- raise ValueError(
- "Specified sender must either be a model or a "
- "model name of the 'app_label.ModelName' form."
- )
- try:
- sender = apps.get_registered_model(app_label, model_name)
- except LookupError:
- ref = (app_label, model_name)
- refs = self.unresolved_references.setdefault(ref, [])
- refs.append((receiver, weak, dispatch_uid))
- return
- super(ModelSignal, self).connect(
- receiver, sender=sender, weak=weak, 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"])
- post_migrate = Signal(providing_args=["app_config", "verbosity", "interactive", "using"])
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