Django Signals Inheriting Signals on Extended Models

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Django's signals are restricted to precise class signatures upon registration, and thus subclassed models are not immediately registered onto the same signal.

Take this model and signal for example

class Event(models.Model):
    user = models.ForeignKey(User)

class StatusChange(Event):

class Comment(Event):

def send_activity_notification(sender, instance: Event, raw: bool, **kwargs):
    Fire a notification upon saving an event

    if not raw:
        msg_factory = MessageFactory(
post_save.connect(send_activity_notification, Event)

With extended models, you must manually attach the signal onto each subclass else they won't be effected.

post_save.connect(send_activity_notification, StatusChange)
post_save.connect(send_activity_notification, Comment)

With Python 3.6, you can leverage some additional class methods build into classes to automate this binding.

class Event(models.Model):

    def __init_subclass__(cls, **kwargs):
        post_save.connect(send_activity_notification, cls)

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