python - 从另一个模型向序列化器添加额外的字段

Question

我将在我的项目中将模型包含到另一个序列化器中，这里是规范。我有一个评论模型如下

class Review(models.Model):
    profile = models.ForeignKey(Profile, on_delete=models.CASCADE)
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    rating= models.ForeignKey(ProductRating, on_delete=models.DO_NOTHING)
    comment = models.TextField()

我的功能是显示用户为产品写的评论数量，我应该像那样在序列化程序中显示

class WishList(models.Model):
    user = models.ForeignKey('authentication.User', on_delete=models.CASCADE, null=True)
    product = models.ForeignKey(Product, on_delete=models.CASCADE, null=True)

serailzier.py

class GetWishlistSerializer(serializers.ModelSerializer):

name = serializers.CharField(source='product.name', read_only=True)
rating = serializers.IntegerField(source='product.rating', read_only=True)
image = serializers.ImageField(source='product.image', read_only=True)
price = serializers.DecimalField(source='product.price', decimal_places=2, max_digits=10, read_only=True)
review = SerializerMethodField()

class Meta:
    model = WishList
    fields = ['user','product', 'name', 'rating', 'image', 'price', 'description', 'review']

def get_review(self, obj):
    return Review.objects.filter(product_id=obj.id).count()

它应该计算指定产品的评论数量，但它没有工作，它给出了这样的结果。

{
            "user": 1,
            "product": 1,
            "name": "Samsung A70",
            "rating": 5,
            "image": "http://localhost:8000/media/products/2019/08/30/wkl6pb_E2RUzH6.jpeg",
            "price": "2500.00",
            "description": "bla bla bla",
            "review": 0
        }

但我有一个关于产品的评论:1 它应该显示 1 但它显示 0 我不知道我在这里遗漏了什么。有什么帮助吗？如果问题不清楚，请告诉我，我会尝试更详细地说明

Answer 1

问题出在查询上。而不是

# comparing it with wishlist pk instead of wishlist's pro
Review.objects.filter(product_id=obj.id).count()

但它应该得到产品审查

def get_review(self, obj):
    return Review.objects.filter(product_id=obj.product.id).count()