django-rest-framwork尝试获取字段值时出现AttributeError [英] django-rest-framwork Got AttributeError when attempting to get a value for field

问题描述

我想通过join product_ratings table获得所有prodcut表值.我做了这样的事情，但是这段代码给了我AttributeError ...我做了

i want get all prodcut table values with join product_ratings table . i did somthing like this but this code give me AttributeError ... i did

product_ratings = ProductRatingSerializer(许多=真)在产品序列化程序中，并在字段中使用了此值，但它不起作用:

product_ratings = ProductRatingSerializer(many=True) in product serializer and used this value in field but it not work:

其完整的错误消息:

Got AttributeError when attempting to get a value for field `product_ratings` on serializer `ProductSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `Product` instance.
Original exception text was: 'Product' object has no attribute 'product_ratings'.

视图:

class StoreApiView(mixins.CreateModelMixin, generics.ListAPIView):
    lookup_field = 'pk'
    serializer_class = ProductSerializer

    def get_queryset(self):
        qs = Product.objects.all()
        query = self.request.GET.get('q')
        if query is not None:
            qs = qs.filter(
                Q(title__icontains=query) |
                Q(description__icontains=query)
            ).distinct()
        return qs

其序列化程序类:

class ProductRatingSerializer(ModelSerializer):
    class Meta:
        model = Product_ratings
        fields = [
            'p_id',
            'commenter',
            'comment',
            'rating',
            'created_date',
        ]
        read_only_fields = ['p_id']


class ProductSerializer(ModelSerializer):
    product_ratings = ProductRatingSerializer(many=True)
    author = serializers.SerializerMethodField()

    def get_author(self, obj):
        return obj.author.first_name
    class Meta:
        model = Product
        fields = [
            'product_id',
            'author',
            'category',
            'title',
            'description',
            'filepath',
            'price',
            'created_date',
            'updated_date',
            'product_ratings',
        ]
        read_only_fields = ['product_id', 'created_date', 'updated_date', 'author']

相关模型类:

class Product(models.Model):
    product_id = models.AutoField(primary_key=True)
    author = models.ForeignKey(User, on_delete=models.CASCADE, db_index=True)
    category = models.ForeignKey(Category, on_delete=models.CASCADE, to_field='cat_id')
    title = models.CharField(max_length=120)
    description = models.TextField(null=True, blank=True)
    price = models.CharField(max_length=50, null=True, blank=True)
    filepath = models.CharField(max_length=100, null=True, blank=True)
    created_date = models.DateTimeField(auto_now_add=True)
    updated_date = models.DateTimeField(auto_now=True)

class Product_ratings(models.Model):
    p_id = models.ForeignKey(Product, on_delete=models.CASCADE, to_field='product_id')
    commenter = models.ForeignKey(User, on_delete=models.CASCADE)
    comment = models.CharField(max_length=200, null=True, blank=True)
    rating = models.IntegerField(null=True, blank=True)
    created_date = models.DateTimeField(auto_now_add=True)

推荐答案

对于您的情况，ForeignKey的默认反向查找名称为< mode> _set 或 product_ratings_set ，因此您需要将 ProductSerializer 中的 product_ratings 字段替换为 product_ratings_set :

Default reverse lookup name for ForeignKey is <mode>_set or product_ratings_set in your case, so you need to replace product_ratings field in ProductSerializer with product_ratings_set:

class ProductSerializer(ModelSerializer):
    product_ratings_set = ProductRatingSerializer(many=True)
    ...
    class Meta:
        model = Product
        fields = [
        ...
        'product_ratings_set'
        ]    

还可以在模型的ForeignKey中添加 related_name ='product_ratings'属性，以更改反向查找名称，在这种情况下，您无需更改序列化程序:

Also you can add related_name='product_ratings' attribute to model's ForeignKey to change reverse lookup name, in this case you don't need too change serializer:

class Product_ratings(models.Model):
    p_id = models.ForeignKey(Product, on_delete=models.CASCADE, to_field='product_id', related_name='product_ratings')

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