#30022: Doc how to combine post_save signal with on_commit to alter a m2m
relation
when saving a model instance
------------------------------------------------+------------------------
Reporter: George Tantiras | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Documentation | Version: 2.1
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Trying to alter a many to many relation when saving a model's instance is
a common use case.
[https://stackoverflow.com/a/53608043/2996101 For example], when creating
a new user or altering an already existing user, programmatically add or
remove groups he should(n't) belong to.
This can be achieved by catching a post save signal and creating a
decorator that uses
[https://docs.djangoproject.com/en/dev/topics/db/transactions/#django.db.transaction.on_commit
on_commit]:
{{{
def on_transaction_commit(func):
''' Create the decorator '''
def inner(*args, **kwargs):
transaction.on_commit(lambda: func(*args, **kwargs))
return inner
@receiver(
post_save,
sender=settings.AUTH_USER_MODEL,
)
@on_transaction_commit
def group_delegation(instance, raw, **kwargs):
do stuff()
}}}
Is it relevant to doc it as an example in the
[https://docs.djangoproject.com/en/dev/ref/signals/#django.db.models.signals.post_save
post_save] signal chapter?
--
Ticket URL: <https://code.djangoproject.com/ticket/30022>
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