Django发布保存信号未更新数据库

Question

我不明白为什么这个信号不起作用。相同的代码可以工作一次，但是之后我从admin中删除了对象，然后再次运行它，然后它停止工作。

@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

您没有调用save()方法，这就是为什么它没有保存的原因。但是我认为这并不是Django的最佳实现。您可以使用update()：

这样简单地尝试

update()

而且，更新每个对象都没有意义，创建了

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'))

的一个实例。可能您应该只更新创建的对象。像这样：

FinancePending

最后，在命名属性和函数名称时，请遵循

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

。

Answer 2

因为仅在调用save（）方法之后才触发信号pep8 style guide。您应该改用post_save。