Django：订单对象取决于两个值

Question

所以我有这个：

class Thread(models.Model):
    first_thread_notification = models.IntegerField(default=0)
    second_thread_notification = models.IntegerField(default=0)

我需要根据 2 个对象的总和对对象进行排序：

class Meta:
    ordering = ['-first_thread_notification' + '-second_thread_notification']

我知道这是不正确的，但我该怎么做？

编辑

class ManagerSum(models.Manager):
    Thread.objects.annotate(
       total=ExpressionWrapper(
       F('first_thread_notification') + F('-second_thread_notification'), 
       output_field=IntegerField(),
       )
    ).order_by('-total')

class Thread(models.Model):
    first_thread_notification = models.IntegerField(default=0)
    second_thread_notification = models.IntegerField(default=0)

    total_notifications = ManagerSum()

class Meta:
    ordering = ['-total_notifications']

这对吗？

Answer 1

您可以使用注解sum them via an F expression.

from django.db.models import IntegerField, ExpressionWrapper
Thread.objects.annotate(
    total=ExpressionWrapper(
        F('first_thread_notification') + F('-second_thread_notification'), 
        output_field=IntegerField(),
    )
).order_by('-total')