Django:如何判断post_save信号是否在新对象上触发？

Question

我需要对Django中新创建的对象进行一些后台后处理.此后处理应仅在新对象上运行,而不是刚刚更新的对象.

我知道在pre_save中我可以检查对象是否有id,如果没有则那么它是一个新对象.但问题是在后处理中我需要访问id(这样我就可以将结果保存回数据库).

我怎么能以干净的方式做到这一点？

Answer 1

看一下docs:https://docs.djangoproject.com/en/stable/ref/signals/#post-save

如果它是一个新对象created,则会设置一个命名参数True.

Answer 2

正如Docs所说,@ seler指出,但举个例子:

def keep_track_save(sender, instance, created, **kwargs):
    action = 'save' if created else 'update'
    save_duplicate((instance.id, instance.__class__.__name__, action))

post_save.connect(keep_track_save, sender=Group)

Answer 3

我只是把它留在这里，也许它会对某人有所帮助。

from django.db import models
from django.db.models.signals import post_save
from django.dispatch import receiver


class Deal(models.Model):
    name = models.CharField(max_length=255)


@receiver(post_save, sender=Deal)
def print_only_after_deal_created(sender, instance, created, **kwargs):
    if created:
        print(f'New deal with pk: {instance.pk} was created.')