DRF：使用现有嵌套对象发布请求

Question

I'm new to Django Rest Framework and nested serializers. I have a ModelSerializer named OrderSerialiser which contains two nested ModelSerializers : ProductSerializer and ClientSerializer.

I want that new instances of the model client and the model product are created (Only if there is no already existing ones) when a post request is sent to the Order CreateAPI. The solution I have found is to override the create method of the OrderSerializer.

It works fine when there is no instances of the client and the product having the same email and sku, but it returns an error saying that there is already existing objects ( client with the same email and a product with the same sku ) in the other case and does not get those existing objects,I noted that the create method in this case is not called , I think that I have to override the serializers.is_valid() method but I didn't figure out what I should do exactly .

models.py

class Client(models.Model):
    email = models.EmailField(
        verbose_name=_('Email address'),
        max_length=255,
        unique=True,
        primary_key=True
    )
    first_name = models.CharField(_('first name'), max_length=30)
    last_name = models.CharField(_('last name'), max_length=30)

class Product(models.Model):
    sku = models.CharField(
        verbose_name=_('SKU'),
        unique=True,
        max_length=120,
        primary_key=True
    )
    name = models.CharField(
        verbose_name=_('Name'),
        max_length=150
    )
    url = models.URLField(
        verbose_name=_('URL'),
        blank=True,
        null=True
    )


class Order(models.Model):
    client = models.ForeignKey(Client)
    products = models.ManyToManyField(
        Product,
        related_name= "orders",
        null=True,
        blank=True,
    )

serializers.py

class ProductSerialiser(serializers.ModelSerializer):
    class Meta:
        model = Product
        fields = ('sku', 'name', 'url')

class ClientSerialiser(serializers.ModelSerializer):
    class Meta:
        model = Client
        fields = ('email','first_name', 'last_name')



class OrderSerializer(serializers.ModelSerializer):
    owner = serializers.ReadOnlyField(source='owner.email')
    client = ClientSerialiser()
    products = ProductSerialiser(many=True, required=False)

    class Meta:
        model = Order
        fields = ('id', 'client', products')

    def create(self, validated_data):
        client_data = validated_data.pop('client')
        try:
            client_instance = Client.objects.get(email=client_data['email'])
        except ObjectDoesNotExist:
            client_instance = Client.objects.create(**client_data)
        if 'products' in validated_data:
            products_data = validated_data.pop('products')
            order_instance = Order.objects.create(client=client_instance, **validated_data)
            for product_data in products_data:
                try :
                    product = Product.objects.get(sku=product_data['sku'])
                except ObjectDoesNotExist:
                    product = Product.objects.create(**product_data)
                product.orders.add(order_instance)
            return order_instance

        order_instance = Order.objects.create(client=client_instance, **validated_data)
        return order_instance

Answer 1

Akamee,

one way I am used to solve this sort of problems is basically to, inside your serializers.py, do

def validate(self, data):
    data = super(YourSerializer, self).validate(data)

    try:
       data['product'] = Product.objects.get(sku='bar')
    except Product.DoesNotExist:
       data['product'] = Product.object.create(sku='bar')

Answer 2

This isn't ideal, but I did find a solution that solved my problem (I'm waiting to accept it as the answer, hoping someone else can do better)

I have eliminated the validators for the field email in ClientSerializer and the field sku in Productserializer , and then checked the existence of objects manually.

modification on serialzers.py

class ProductSerialiser(serializers.ModelSerializer):
    class Meta:
        model = Product
        fields = ('sku', 'name', 'url')
        extra_kwargs = {
            'sku': {
                'validators': []
            }
        }

class ClientSerialiser(serializers.ModelSerializer):
    class Meta:
        model = Client
        fields = ('email', 'first_name', 'last_name')
        extra_kwargs = {
            'email': {
                'validators': []
            }
        }



class OrderSerializer(serializers.ModelSerializer):
    owner = serializers.ReadOnlyField(source='owner.email')
    client = ClientSerialiser(partial=True)
    products = ProductSerialiser(many=True, required=False, partial=True)

    class Meta:
        model = Order
        fields = ('id','client', products')


    def create(self, validated_data):
        client_data = validated_data.pop('client')
        try:
            print "**************** client exists ***********************"
            client_instance = Client.objects.get(email=client_data['email'])
        except ObjectDoesNotExist:
            print "**************** creating a client    ***********************"
            client_instance = Client.objects.create(**client_data)
        if 'products' in validated_data:
            products_data = validated_data.pop('products')
            order_instance = Order.objects.create(client=client_instance, **validated_data)
            for product_data in products_data:
                try :
                    print "**************** Product exists ***********************"
                    product = Product.objects.get(sku=product_data['sku'])
                except ObjectDoesNotExist:
                    print "**************** creating object product ***********************"
                    product = Product.objects.create(**product_data)
                product.orders.add(order_instance)
            return order_instance

        order_instance = Order.objects.create(client=client_instance, **validated_data)
        return order_instance