如何限制嵌套序列化给定的对象数

Question

Store具有SimilarStore的外键。通常，similarstore_set中大约有一百家类似的商店。当我使用similarstore_set制作API时，是否有一种方法可以限制Django REST Framework中类似存储的数量？

serializer.py

class SimilarStoreSerializer(ModelSerializer):

    class Meta:
        model = SimilarStore
        fields = ('domain', )


class StoreSerializer(ModelSerializer):

    similarstore_set = SimilarStoreSerializer(many=True)

    class Meta:
        model = Store
        fields = '__all__'

更新

以下代码抛出'Store' object has no attribute 'similarstores_set'，实际上却有similarstore_set，为什么抛出错误？

class StoreSerializer(ModelSerializer):

    image_set = ImageSerializer(many=True)
    promotion_set = PromotionSerializer(many=True)

    similar_stores = SerializerMethodField()

    def get_similar_stores(self, obj):
        # get 10 similar stores for this store
        stores = obj.similarstores_set.all()[:10]  <-- This line throws the error
        return SimilarStoreSerializer(stores, many=True).data

    class Meta:
        model = Store
        fields = '__all__'

Answer 1

您可以为serializers.SerializerMethodField()添加一个similarstore_set并定义一个查询SimilarStore数据并设置similarstore_set的方法。您可以通过将上下文传递给序列化器来传递similarstore_set中所需的元素数。参见https://www.django-rest-framework.org/api-guide/serializers/#including-extra-context

Answer 2

您可以使用执行自定义查找并限制记录数：

class StoreSerializer(ModelSerializer):
    similar_stores = serializers.SerializerMethodField()

    def get_similar_stores(self, obj):
        stores = obj.similarstore_set.all()[:10] # get 10 similar stores for this store
        return SimilarStoreSerializer(stores, many=True).data

    class Meta:
        model = Store
        fields = '__all__'