from functools import partial from django.db.models.utils import make_model_tuple from django.dispatch import Signal class_prepared = Signal() 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(use_caching=True) post_init = ModelSignal(use_caching=True) pre_save = ModelSignal(use_caching=True) post_save = ModelSignal(use_caching=True) pre_delete = ModelSignal(use_caching=True) post_delete = ModelSignal(use_caching=True) m2m_changed = ModelSignal(use_caching=True) pre_migrate = Signal() post_migrate = Signal()