Sort django signal's receivers

问题

Django calls receiver methods in its own way. Is there any way that we can sort the receivers of Django signal? I didn't find anything related to it in official Django documentation.

回答1:

Unless I'm mistaken, there isn't any reason to have more than one receiver for the same signal and sender. It is possible but I don't believe it is the right way to approach it and you will not have explicit control over the calling sequence of each.

If, for example, you have a set of duplicate signals (that do different things) like so:

from django.db.models import signals
from django.dispatch import receiver
from django.contrib.auth import get_user_model


User = get_user_model()


@receiver(signals.pre_save, sender=User)
def signal_receiver_1(*args, **kwargs):
    pass

@receiver(signals.pre_save, sender=User)
def signal_receiver_2(*args, **kwargs):
    pass

@receiver(signals.pre_save, sender=User)
def signal_receiver_3(*args, **kwargs):
    pass

That would work but the order of execution isn't explicitly known. However, you could rewrite it to something like this to explicitly state the order of execution:

from django.db.models import signals
from django.dispatch import receiver
from django.contrib.auth import get_user_model


User = get_user_model()


def signal_receiver_1(*args, **kwargs):
    pass

def signal_receiver_2(*args, **kwargs):
    pass

def signal_receiver_3(*args, **kwargs):
    pass

@receiver(signals.pre_save, sender=User):
def pre_save_signal_receiver_master(*args, **kwargs):
    signal_receiver_1(*args, **kwargs)
    signal_receiver_2(*args, **kwargs)
    signal_receiver_3(*args, **kwargs)

回答2:

https://docs.djangoproject.com/en/2.2/topics/signals/#listening-to-signals

"All of the signal’s receiver functions are called one at a time, in the order they were registered."

Try:

@receiver(signals.pre_save, sender=User)
def signal_receiver_1(*args, **kwargs):
    print('RECEIVER 1')

@receiver(signals.pre_save, sender=User)
def signal_receiver_2(*args, **kwargs):
    print('RECEIVER 2')

@receiver(signals.pre_save, sender=User)
def signal_receiver_3(*args, **kwargs):
    print('RECEIVER 3')

Output will be:

RECEIVER 1
RECEIVER 2
RECEIVER 3

And then mix it up...

来源：https://stackoverflow.com/questions/52084499/sort-django-signals-receivers

标签

python

django

signals