python - Django Rest框架中多对多中间模型的实现方法

Question

• 我想听听您的意见，这种方法正确吗？
• 如何更好地序列化 m2m 中间模型？
• 我想知道如何组合 Display 和 Create 序列化器。
• models.py

class Material(models.Model):
    name = models.CharField(max_length=120)   


class Product(models.Model):
    name = models.CharField(max_length=120)
    materials = models.ManyToManyField(Material, through='MaterialProduct')


class MaterialProduct(models.Model):
    material = models.ForeignKey(Material, on_delete=models.CASCADE)
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    rate = models.FloatField(default=100)

• views.py

class Products(APIView):
    def get(self, request, format=None):
        products = Product.objects.all()
        serializer = ProductDisplaySerializer(products, many=True) # Display
        return Response(serializer.data)

    def post(self, request, format=None):
        serializer = ProductCreateSerializer(data=request.data) # Create
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

• serializers.py

class MaterialSerializer(serializers.ModelSerializer):
    class Meta:
        model = Material
        fields = '__all__'


class ProductMaterialRateSerializer(serializers.ModelSerializer):
    material = MaterialSerializer(read_only=True)
    material_id = serializers.PrimaryKeyRelatedField(
        write_only=True, source='material', queryset=Material.objects.all())

    class Meta:
        model = MaterialProduct  # attention!!!
        fields = ('material', 'material_id', 'rate')


class ProductCreateSerializer(serializers.ModelSerializer):
    '''To create a product with existed material and a material rate(extra field) '''
    materials = ProductMaterialRateSerializer(many=True)

    class Meta:
        model = Product
        fields = ('id', 'name', 'materials')

    def create(self, validated_data):

        materials_data = validated_data.pop('materials')
        product = Product.objects.create(**validated_data)
        for material_data in materials_data:
            MaterialProduct.objects.create(
                product=product,
                material=material_data.get('material'),
                rate=material_data.get('rate'))
        return product

• 显示的数据:

 {
        "id": 29,
        "name": "product 4",
        "materials": [
            {
                "material_id": 3,
                "rate": 30
            },
            {
                "material_id": 2,
                "rate": 70
            }
        ]
    }

创建要发送的数据:

{
    "name" : "product 4",
    "materials" : [
        {
            "material_id":3,
            "rate" : 30
        }   
        ,{
            "material_id":2,
            "rate" : 70
        }

    ]
}

创建后返回的数据:

• 注意:它正确保存了数据，但不显示如下!

{
    "id": 29,
    "name": "product 4",
    "materials": [
        {},
        {}
    ]
}

Answer 1

您可以使用RetrieveAPIView用于显示和 CreateAPIView for create 是内置功能，可以使事情变得更简单，并且其他开发人员可以更轻松地使用您的代码，因为他们需要熟悉的是 DRF 的工作方式，而不是您编写代码的方式。基本上最好遵循其他开发人员熟悉的模式。

我不建议组合创建和显示序列化器，除非它们非常简单。如果它们变得有点复杂，那么调试或进行更改可能会变得困难，特别是当其他人正在调试您的代码时!

对于序列化 m2m，materials = ProductMaterialRateSerializer(many=True)是正确的方法，为了创建，您可以使用内置功能，但如果它很复杂并且需要一些计算，那么我建议覆盖 save和update创建序列化程序中的方法。

对于返回的数据:

您可以像这样覆盖上下文:

def post(self, request, format=None):
    serializer = ProductCreateSerializer(data=request.data) # Create
    if serializer.is_valid():

        # Get the saved object
        saved_obj = serializer.save()

        # Serialize the saved object with the preferred serializer.
        response_data = ProductDisplaySerializer(saved_obj).data

        return Response(response_data, status=status.HTTP_201_CREATED)
    return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)