Django，更新率，信号

Question

class Thing (model.Models):
    name = models.CharField(max_length = 222)
    ratee = models.IntegerField(default = 0)
    ...
class Rate(models.Model):
    thing = models.ForeignKey(Thing)
    user = models.ForeignKey(User)
    rate = models.IntegerField()

如果用户评估事物(给出速率(，我想自动计算平均水平并保存以在物品中。如何制作？

Answer 1

你可以做

class Rate(models.Model):
    def save(self, *args, **kwargs):
        super(Rate, self).save(*args, **kwargs)
        self.thing.ratee = Rate.objects.filter(thing=self.thing).aggregate(Avg('rate'))["rate__avg"]
        self.thing.save()

Answer 2

如果要使用信号，则可以执行以下

from django.dispatch import receiver
from django.db.models.signals import post_save
from django.db.models import Avg
@receiver(post_save, sender=Rate, dispatch_uid="update_rating")
def update_rating(sender, instance, **kwargs):
     # Logic to update the rating goes here, for example...
     avg = Rate.objects.filter(thing=instance.thing) 
                       .aggregate(Avg('rate')).values()[0]
     instance.thing.ratee = avg
     instance.thing.save()

另外，您可以覆盖Rate中的save方法在没有信号的情况下执行此操作。看起来更像：

class Rate(models.Model):
    # ...
    def save(self, *args, **kwargs):
        super(Rate, self).save(*args, **kwargs)
        # Logic to update the average rating here