#9318: "Virtual" behaviour for signal dispatcher and model inheritance
-------------------------------------+-------------------------------------
Reporter: Alexander Artemenko | Owner: (none)
Type: New feature | Status: new
Component: Core (Other) | Version: 1.0
Severity: Normal | Resolution:
Keywords: model inheritance, | Triage Stage: Accepted
signals, dispatch, proxy, |
subclass |
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by rgangopadhya):
To handle pre_save and all other signals, I took the approach of sending
all signals to the parent model when triggered by child models:
{{{
from django.db import models
from django.db.models.signals import (
pre_save,
post_save,
pre_delete,
post_delete,
m2m_changed,
)
class A(models.Model): pass
class B(A):
class Meta:
proxy = True
signals = [
pre_save,
post_save,
pre_delete,
post_delete,
m2m_changed,
]
def make_sender_fn(model, signal):
def sender_fn(sender, **kwargs):
# signal send method passes itself
# as a signal kwarg to its receivers
kwargs.pop('signal')
signal.send(sender=model, **kwargs)
return sender_fn
def connect_all_signals(from_model, to_model):
# connecting signals from one model to another
# is useful when from_model inherits from to_model
# and hence should take on all behavior from the
# parent model
# Django does not send signals for parent model
# when child is triggered
# https://code.djangoproject.com/ticket/9318#no1
for signal in signals:
signal.connect(
make_sender_fn(to_model, signal),
sender=from_model,
weak=False,
)
connect_all_signals(B, A)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/9318#comment:37>
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