Reuse Existing Object in Django Rest Framework Nested Serializer

Question

How do I go about re-using the referenced object when using nested Serializers in the drf:

Let's say I have the following two Models:

class Address(models.Model):
    address_line = models.CharField(max_length=45)

class Person(models.Model):
    name = models.CharField(max_length=45)
    address = models.ForeignKey(Address)

with Serializers:

class AddressSerializer(serializers.ModelSerializer):
    class Meta:
        model = Address

class PersonSerializer(serializers.ModelSerializer):
    address = AddressSerializer()

    class Meta:
        model = Person

Right now the Serializers handle creating both the Address and the Person together. e.g, when I post the following:

{
    'name': 'Alex',
    'address': {
        'address_line': "1 Here"
    }
}

a Person is created and an Address is created with the Person pointing to the newly created Address.

What is the best way to NOT create a new Address but to reuse an existing Address if there is already an Address with a given address_line? i.e if I wanted to make the address_line field unique? (this object re-use is sometimes called "interning")

What about if there were two address fields address_line1 and address_line2 and I wanted to reuse the Address object if there already exists an Address with both of those fields (i.e. unique_together=(address_line1, address_line2))?

Answer 1

Recently I faced a similar problem, solved it using the following approach (the code has not been tested, its just for reference):

class PersonSerializer(serializers.ModelSerializer):
    address = AddressSerializer()

    class Meta:
        model = Person

    def create(self, validated_data):
        # pop the validated user data
        # assuming its a required field,
        # it will always be there in validated_data
        address = validated_data.pop('address')

        try:
            address = Address.objects.get(address_line=address.get('address_line'))
        except ObjectDoesNotExist:
            address_serializer = AddressSerializer(data=address)
            address_serializer.is_valid(raise_exception=True)
            address = address_serializer.save()
        else:
            # save the user and update the validated_data for setting up profile
            validated_data['address'] = address

        return super(PersonSerializer, self).create(validated_data)

Hope this helps :)