How to save three related models in one DRF endpoint?

Question

I have 4 related models and I need to implement the functionality to consistently create instances of these models in a database in one post query. For this I use override of the APIView class post method.

models

class VendorContacts(models.Model):
    contact_id = models.AutoField(primary_key=True)
    vendor = models.OneToOneField('Vendors', on_delete=models.CASCADE)
    contact_name = models.CharField(max_length=45, blank=True)
    phone = models.CharField(max_length=45, blank=True)
    email = models.CharField(max_length=80, blank=True, unique=True)

    class Meta:
        db_table = 'vendor_contacts'


class VendorModuleNames(models.Model):
    vendor = models.OneToOneField('Vendors', on_delete=models.CASCADE, primary_key=True)
    module = models.ForeignKey(Modules, models.DO_NOTHING)
    timestamp = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = 'vendor_module_names'
        unique_together = (('vendor', 'module'),)


class Vendors(models.Model):
    COUNTRY_CHOICES = tuple(COUNTRIES)

    vendorid = models.AutoField(primary_key=True)
    vendor_name = models.CharField(max_length=45, unique=True)
    country = models.CharField(max_length=45, choices=COUNTRY_CHOICES)
    nda = models.DateField(blank=True, null=True)
    user_id = models.ForeignKey('c_users.CustomUser', on_delete=models.PROTECT)
    timestamp = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = 'vendors'
        unique_together = (('vendorid', 'timestamp'),)

class Modules(models.Model):
    MODULES_NAME =tuple(MODULES)
    mid = models.AutoField(primary_key=True)
    module_name = models.CharField(max_length=50, choices=MODULES_NAME)
    active = models.BooleanField(default=True)
    timestamp = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = 'modules'
        unique_together = (('mid', 'timestamp'),)

serializer.py

class VendorsSerializer(serializers.ModelSerializer):
    class Meta:
        model = Vendors
        fields = ('vendor_name',
                  'country',
                  'nda',)


class VendorContactSerializer(serializers.ModelSerializer):
    class Meta:
        model = VendorContacts
        fields = (
                  'contact_name',
                  'phone',
                  'email',)


class VendorModulSerializer(serializers.ModelSerializer):
    class Meta:
        model = VendorModuleNames
        fields = ('module',)


class ModulesSerializer(serializers.ModelSerializer):
    class Meta:
        model = Modules
        fields = ('module_name', )

views.py

class VendorsCreateView(APIView):
    """Create new vendor instances from form"""

    def post(self, request, *args, **kwargs):
        vendor_serializer = VendorsSerializer(data=request.data)
        vendor_contact_serializer = VendorContactSerializer(data=request.data)
        vendor_modules_serializer = VendorModulSerializer(data=request.data)
        module_serializer = ModulesSerializer(data=request.data)
        try:
            vendor_serializer.is_valid(raise_exception=True) \
                and vendor_contact_serializer.is_valid(raise_exception=True) \
                and vendor_modules_serializer.is_valid(raise_exception=True) \
                and module_serializer.is_valid(raise_exception=True)
            vendor_serializer.save(user_id=request.user)
            # ....
            # Some new logic here ????
            # ...
        except ValidationError:
            return Response({"errors": (vendor_serializer.errors,
                                        vendor_contact_serializer.errors,
                                        vendor_modules_serializer.errors
                                        )},
                            status=status.HTTP_400_BAD_REQUEST)
        else:
            return Response(request.data, status=status.HTTP_200_OK)

There is no problem saving one Vendor model, but I can't imagine how to save cascading all related models in a single request.

Answer 1

save returns the newly saved object, which you can then pass into the subsequent save() methods:

vendor = vendor_serializer.save(user_id=request.user)
module = module_serializer.save()
vendor_module = vendor_modules_serializer.save(module=module, vendor=vendor)
vendor_contact = vendor_contact_serializer.save(vendor=vendor)