How to serialize an extended user?

[AhmadM-DL]

I am building an API based application.
Users register through an API.
For registration an extended user model has been written as proposed by Django documentation:

class UserProfile(models.Model):
    user = models.OneToOneField(User, on_delete= models.CASCADE)
    phone_number = models.CharField(max_length=25, unique=True, validators=[RegexValidator(r"^\+(?:[0-9] ?){6,14}[0-9]$")])
    language_preferences = models.CharField(max_length= 35)

How to write the signup view and serializer for this model?

[browniebroke]

I've got a similar profile in a Django project and I chose to write a RegisterSerializer around the User model, that creates the profile instance with extra attributes:

class RegisterSerializer(UserSerializer):

	# Profile fields
    phone_number = serializers.CharField(source="profile.phone_number")
    language_preferences = serializers.CharField(source="profile.language_preferences")

    class Meta:
        model = User
        read_only_fields = ["id"]
        fields = read_only_fields + [
            "first_name",
            "last_name",
            "email",
            "password",
            "phone_number",
            "language_preferences",
        ]
        extra_kwargs = {
            "password": {"write_only": True},
        }

    def create(self, validated_data):
        # Hash password before saving
        raw_password = validated_data["password"]
        validated_data["password"] = make_password(raw_password)

        # Extract profile fields from validated data
        phone_number = validated_data.pop("phone_number", None)
        language_preferences = validated_data.pop("language_preferences", None)

        user = super().create(user_data)

        # Create profile instance once the user is created
        profile = UserProfile.objects.create(
            user=user,
            phone_number=phone_number,
            language_preferences=language_preferences,
        )
        return user

Alternatively, you could also:

• Do the opposite: place User fields on a UserProfile, keeping a flat structure.
• Have a nested UserSerializer inside a UserProfileSerializer, but that's kind of leaking the UserProfile abstraction to your frontend(s), which may not be desirable...

[AhmadM-DL]

I end up doing this:

class UserProfileSerializer(serializers.ModelSerializer):
    class Meta:
        model = UserProfile
        fields = ['phone_number', 'language_preferences']

class UserSerializer(serializers.ModelSerializer):
    profile = UserProfileSerializer()

    class Meta:
        model = User
        fields = ('username', 'email', 'first_name', 'last_name', 'password', 'profile')
        extra_kwargs = {'password': {'write_only': True}}

    def create(self, validated_data):
        profile_data = validated_data.pop('profile')
        password = validated_data.pop('password')
        user = User.objects.create(**validated_data)
        user.set_password(password)
        user.save()
        UserProfile.objects.create(user=user, **profile_data)
        return user

From what I see DRF is very optionated which doesn't help when you want to implement best practices.

[AhmadM-DL]

Source Argument Documentation: https://www.django-rest-framework.org/api-guide/fields/#source