Django post 保存信号不更新数据库

Question

我不明白为什么这个信号不起作用。同样的代码工作了一次，但之后我从管理员中删除了对象并再次运行它停止工作。

@receiver(post_save, sender=FinancePending)
def calcualate_FinancePending(sender, instance, created, **kwargs):
amount_paid = FinancePending.objects.values_list('amountPaid', flat=True)
amount_paid = list(amount_paid)
total_amount = FinancePending.objects.values_list('TotalAmount', flat=True)
total_amount = list(total_amount)

# total - paid
TotalFee = [int(s.replace(',', '')) for s in total_amount]
AmountPaid = [int(s.replace(',', '')) for s in amount_paid]
finance_pending = FinancePending.objects.all()
i = 1

while i <= len(TotalFee):
    amount_pending = TotalFee[i-1] - AmountPaid[i-1]
    amountpending = FinancePending.objects.filter(invoiceNumber=i)
    amountpending.AmountPending = amount_pending
    i = 1 + i

Answer 1

因为信号 post_save only triggered after call save() method. You should use post_delete 而不是。

Answer 2

您没有调用 save() 方法，这就是它没有保存的原因。但我不认为它是django prespective 的优化实现。你可以简单地尝试使用 update():

from django.db.models import F

@receiver(post_save, sender=FinancePending)
def calcualate_FinancePending(sender, instance, created, **kwargs):
    FinancePending.objects.update(AmountPending=F('TotalAmount')-F('amountPaid'))

此外，更新每个创建 FinancePending 实例的对象是没有意义的。可能你应该只更新创建的对象。像这样：

@receiver(post_save, sender=FinancePending)
def calcualate_FinancePending(sender, instance, created, **kwargs):
    instance.AmountPending=instance.TotalAmount-instance.amountPaid
    instance.save()

最后，请在命名属性和函数名称时遵循pep8 style guide。

Django post 保存信号不更新数据库

Django post save signal not updating the database

python

django

django-signals

django-models