如何在Django視圖中基於外鍵過濾模型數據？

Question

我有兩個模型，分別是User和UserRating，它們之間是一對多的關系，如何過濾特定用戶的評分，以便可以計算出其總體評分並將其顯示在個人資料中。 謝謝。

#this is model for user
class User(models.Model):
    username = models.CharField(max_length=128, unique=True)
    email = models.EmailField(max_length=128, unique=True)
    #password = forms.CharField(max_length=32, widget=forms.PasswordInput)
    profilepic = models.ImageField(null=True)
    firstname = models.CharField(max_length=128, null=True)
    secondname = models.CharField(max_length=128, null=True)
    city = models.ForeignKey(City)


#this is the model for user ratings - one to many relationship with User
class UserRating(models.Model):
    user = models.ForeignKey(User)
    comment = models.CharField(max_length=500)
    rating = models.IntegerField(default=5)

Answer 1

如果您有一個User對象，則可以通過反向關系訪問其所有評分：

user.userrating_set.all()

要計算他的平均評分，請使用Aggregation

from django.db.models import Avg
user.userrating_set.all().aggregate(Avg('rating'))

編輯

如果要將其作為用戶模型的屬性，請執行以下操作：

class User(models.Model):
    username = models.CharField(max_length=128, unique=True)
    ... 

    @property
    def avg_rating(self):
        return self.userrating_set.all().aggregate(Avg('rating'))

然后您可以使用

user.avg_rating

Answer 2

編輯 -已更新，因此您可以除以評分數

在視圖中...

from django.db.models import Sum

current_user_rating_object = UserRating.objects.filter(user=request.user)
ratings = current_user_rating_objects.count()
total_rating = current_user_rating_object.aggregate(Sum(total_rating=Sum('rating', distinct=True))['total_rating']
weighted_rating = total_rating / ratings