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()
If user evaluate the thing(give rate in Rate), I want to automatically calculate average and save to ratee in Thing. How to make it?
If you want to use a signal, you can do the following
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()
Alternatively, you can override the save method in Rate to do this without signals. That would look more like:
class Rate(models.Model):
# ...
def save(self, *args, **kwargs):
super(Rate, self).save(*args, **kwargs)
# Logic to update the average rating here
You can do
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()