django rest-framework 嵌套关系使用过滤器

Question

使用django rest-farmework实现API，有个问题一直无法解决：如何过滤关联表？，具体代码如下：

models.py

class Category(models.Model):
    name = models.CharField(max_length=30)
    amount = models.IntegerField()

class Source(models.Model):
    name = models.CharField(max_length=50)
    rss_link = models.URLField()
    amount = models.IntegerField()
    # ForeignKey
    category = models.ForeignKey(Category)

views.py

class CategoryListView(APIView):
    def get(self, request):
        category = Category.objects.all()
        serializers = CategorySerializers(category, many=True)
        return Response(serializers.data)

serializers.py

class SourceSerializers(serializers.ModelSerializer):
    class Meta:
        model = Source
        fields = ("id","name","amount")

class CategorySerializers(serializers.ModelSerializer):
    source_set = SourceSerializers(many=True, read_only=True)

    class Meta:
        model = Category
        fields = ("id","name","amount","source")

程序运行结果：

[
    {
        "id": 1,
        "name": "study",
        "amount": "0",
        "source": [
            {
                "id": 34,
                "name": "java",
                "amount": "0"
            },
            {
                "id": 35,
                "name": "python",
                "amount": "0"
            },
            {
                "id": 36,
                "name": "css",
                "amount": "2"
            }
        ]
    }
]

现在我只需要查询0条数据的"amount"的"source"，我试过这样写代码：

serializers.py

class SourceSerializers(serializers.ModelSerializer):
    class Meta:
        model = Source
        fields = ("id","name","amount")

class CategorySerializers(serializers.ModelSerializer):

    #Modified the following code
    source_set = SourceSerializers(Source.objects.filter(amount=0),many=True, read_only=True)

    class Meta:
        model = Category
        fields = ("id","name","amount","source")

修改以下代码：

source_set = SourceSerializers(many=True, read_only=True)

到

source_set = SourceSerializers(Source.objects.filter(amount=0),many=True, read_only=True)

但是结果是一样的，希望结果是：

[
    {
        "id": 1,
        "name": "study",
        "amount": "0",
        "source": [
            {
                "id": 34,
                "name": "java",
                "amount": "0"
            },
            {
                "id": 35,
                "name": "python",
                "amount": "0"
            }
        ]
    }
]

提前致谢。

Answer 1

稍微更改一下序列化程序。您可以有一个序列化相关类别对象的 SourceWithCategorySerializer。然后，您可以根据数量查询 Source 对象并将该 QuerySet 传递给您的序列化程序。

您的看法：

class CategoryListView(APIView):
    def get(self, request):
        sources = Source.objects.filter(amount=0)
        serializers = SourceWithCategorySerializers(sources, many=True)
        return Response(serializers.data)

序列化程序：

class SourceWithCategorySerializers(serializers.ModelSerializer):
    category = CategorySerializer(read_only=True)

    class Meta:
        model = Source
        fields = ("id","name","amount", "category")

class CategorySerializers(serializers.ModelSerializer):
    class Meta:
        model = Category
        fields = ("id","name","amount")

Answer 2

您可以使用 SerializerMethodField:

class CategorySerializer(serializers.ModelSerializer):
    source_set = serializers.SerializerMethodField('get_sources')

    def get_sources(self, category):
        sources = category.source_set.filter(amount=0)
        return SourceSerializer(instance=sources, many=True).data

    class Meta:
        model = Category
        fields = ("id", "name", "amount", "source")

我从你的 class 名字中删除了复数 's' 因为它们让我很痒 ;)

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