Django Rest Framework Many To Many Intermediate Table Serialization Example

• models.py

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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)

• urls.py

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from django.urls import path
# internal
from my.views import Products, Materials
​
urlpatterns = [   
    # many to many intermediate using
    path('products', Products.as_view()),
    path('materials', Materials.as_view()),
    ]

• views.py

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from rest_framework.views import APIView
from rest_framework import status
from rest_framework.response import Response
​
# internal
from my.models import Product, Material, MaterialProduct
from my.serializers import ProductDisplaySerializer, ProductCreateSerializer, MaterialSerializer
​
​
class Products(APIView):
    def get(self, request, format=None):
        products = Product.objects.all()
        serializer = ProductDisplaySerializer(products, many=True)
        return Response(serializer.data)
​
    def post(self, request, format=None):
        serializer = ProductCreateSerializer(data=request.data)
        if serializer.is_valid():
            saved_obj = serializer.save()
            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)
        
class Materials(APIView):
    def get(self, request, format=None):
        products = Material.objects.all()
        serializer = MaterialSerializer(products, many=True)
        return Response(serializer.data)
​
    def post(self, request, format=None):
        serializer = MaterialSerializer(data=request.data)
        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

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from rest_framework import serializers
# internal
from my.models import Product, Material, MaterialProduct
​
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
​
​
class MaterialProductSerializer(serializers.ModelSerializer):
​
    class Meta:
        model = MaterialProduct
        fields = ('material_id', 'rate')
​
​
class ProductDisplaySerializer(serializers.ModelSerializer):
    '''To display product with related materials '''
    materials = serializers.SerializerMethodField()
​
    class Meta:
        model = Product
        fields = ('id', 'name', 'materials')
​
    def get_materials(self, product_instance):
        query_datas = MaterialProduct.objects.filter(product=product_instance)
        return [MaterialProductSerializer(material).data for material in query_datas]
​

• POST request data:

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{
    "name" : "product 5",
    "materials" : [
        {
            "material_id":1,
            "rate" : 30
        }   
        ,{
            "material_id":2,
            "rate" : 70
        }
    ]
}

• Returned:

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{
    "id": 30,
    "name": "product 5",
    "materials": [
        {
            "material_id": 1,
            "rate": 30
        },
        {
            "material_id": 2,
            "rate": 70
        }
    ]
}

• GET request

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[
    {
        "id": 29,
        "name": "product 4",
        "materials": [
            {
                "material_id": 3,
                "rate": 30
            },
            {
                "material_id": 2,
                "rate": 70
            }
        ]
    },
    {
        "id": 30,
        "name": "product 5",
        "materials": [
            {
                "material_id": 1,
                "rate": 30
            },
            {
                "material_id": 2,
                "rate": 70
            }
        ]
    }
]