How to use Django model inheritance with signals?

Question

I have a few model inheritance levels in Django:

class WorkAttachment(models.Model):
    \"\"\" Abstract class that holds all fields that are required in eac         


        

Answer 1

Michael Herrmann's solution is definitively the most Django-way of doing this. And yes it works for all subclasses as they are loaded at the ready() call.

I would like to contribute with the documentation references :

In practice, signal handlers are usually defined in a signals submodule of the application they relate to. Signal receivers are connected in the ready() method of your application configuration class. If you’re using the receiver() decorator, simply import the signals submodule inside ready().

https://docs.djangoproject.com/en/dev/topics/signals/#connecting-receiver-functions

And add a warning :

The ready() method may be executed more than once during testing, so you may want to guard your signals from duplication, especially if you’re planning to send them within tests.

https://docs.djangoproject.com/en/dev/topics/signals/#connecting-receiver-functions

So you might want to prevent duplicate signals with a dispatch_uid parameter on the connect function.

post_save.connect(my_callback, dispatch_uid="my_unique_identifier")

In this context I'll do :

for subclass in get_subclasses(WorkAttachment):
    post_save.connect(update_attachment_count_on_save, subclass, dispatch_uid=subclass.__name__)

https://docs.djangoproject.com/en/dev/topics/signals/#preventing-duplicate-signals

Answer 2

post_save.connect(my_handler, ParentClass)
# connect all subclasses of base content item too
for subclass in ParentClass.__subclasses__():
    post_save.connect(my_handler, subclass)

have a nice day!