Creating instances of 2 related models using nested serializer in Django

Question

I am a newbie at Django and I have come across this problem with my code. I have a Custom User Model and an Account model which are related by many-to-many field.

During SignUp a user is asked to either create an Account or not ( join other account through a link ).

• If the User creates an Account then he is the owner of the account and other Users can join the account.(Did not finish the code for ownership)
• One User can be a part of several accounts at the same time.
• Creation of Account(or not) and the User takes place in the Signup view.

I read up about the nested serializer in the documentation and i think this should create the two models instances. How to create relationships in one view using nested serializers? Other Approaches to solve the issue?

Models

class Account(models.Model):
    AccountName = models.TextField(max_length=100, blank=False, null=False)

class User(AbstractBaseUser):
    AccountName = models.ManyToManyField(Account)
    CreateAccount = models.BooleanField(blank=False, null=False)
    EmailId = models.EmailField(max_length=128, blank=False, null=False, unique=True)

    is_admin = models.BooleanField(default=False)
    is_active = models.BooleanField(default=True)
    is_staff = models.BooleanField(default=False)
    is_superuser = models.BooleanField(default=False)

    USERNAME_FIELD = 'EmailId'
    REQUIRED_FIELDS = ['AccountName', 'CreateAccount',]

    # Implemented the other req. functions

    objects = MyAccountManager()

Serializers

class AccountCreationSerializer(ModelSerializer):
    class Meta:
        model = Account
        fields = ['AccountName']

class SignUpSerializer(ModelSerializer):

    AccountName = AccountCreationSerializer()

    class Meta:
        model = User
        fields = ['EmailId', 'AccountName', 'CreateAccount', 'password']
        extra_kwargs = {'password': {'write_only': True, 'required': True}}

    def create(self, validated_data):
        AccountName = validated_data.pop('AccountName')

        if validated_data['CreateAccount']: #Create only when this is True
            Account.objects.create(AccountName=AccountName, **AccountName)

        userAcc = User.objects.create_user(**validated_data)

        return userAcc

View

class SignUpView(APIView):

    def post(request):
        # to edit
        signup_serializer = SignUpSerializer(data=request.data)
        
        # rest of the view

The request // Ignoring the quotes

EmailID: xyz@gmail.com
AccountName: TestAcc
CreateAccount: False
Password: ****

Error: Direct assignment to the forward side of a many-to-many set is prohibited. Use AccountName.set() instead.

Create_user in Custom model

    def create_user(self, EmailId, AccountName, CreateAccount, password):
        if not EmailId:
            raise ValueError("Users must have an email")

        user = self.model(
            EmailId=self.normalize_email(EmailId),
            AccountName=AccountName,
            CreateAccount=CreateAccount,
        )

        user.set_password(password)
        user.save(using=self._db)
        return user

I am pretty sure I am making some mistake regarding the manytomany field but haven't been able to figure out the solution. Any help would be of benefit to me. TIA!

Answer 1

You can not save value directly to many-to-many field. Database does not allow you to do so. It only allows you to add them for associating the relationship between the two tables ( i.e User, Account ). Replace your code segment for Serializer file with the following one.

class AccountCreationSerializer(ModelSerializer):
    class Meta:
        model = Account
        fields = ['AccountName']


class SignUpSerializer(ModelSerializer):
    AccountName = serializers.SerializerMethodField()

    class Meta:
        model = User
        fields = ['EmailId', 'AccountName', 'CreateAccount', 'password']
        extra_kwargs = {'password': {'write_only': True, 'required': True}}

    def validate(self, attrs):
        attrs = super(SignUpSerializer, self).validate(attrs=attrs)
        attrs.update({"AccountName": self.initial_data.get("AccountName")})
        return attrs

    def create(self, validated_data):
        AccountName = validated_data.pop('AccountName')
        acc = Account.objects.create(AccountName=AccountName) if "CreateAccount" in validated_data and validated_data['CreateAccount'] else None

        userAcc = User.objects.create_user(**validated_data)
        if acc:
            userAcc.AccountName.add(acc)

        return userAcc

Finally, replace your SignUpView class in the following way:

class SignUpView(APIView):
    serializer_class = SignUpSerializer

    def post(self, request, *args, **kwargs):
        serializer = self.serializer_class(data=request.data)
        is_valid_serializer = serializer.is_valid(raise_exception=True)
        if is_valid_serializer:
            with transaction.atomic():
                serializer.save()
        # Rest of your code segments to finalize the response

UPDATE

There is a problem with your create_user method. You are here passing the many-to-many field reference (AccountName), which you shouldn't. As I mentioned earlier, you can not save directly many-to-many field. You just need to associate the relation between them. Omit that and it will work!!!

Follow this new definition for this method (create_user).

    def create_user(self, EmailId, CreateAccount, password):
        if not EmailId:
            raise ValueError("Users must have an email")

        user = self.model(EmailId=self.normalize_email(EmailId), CreateAccount=CreateAccount)

        user.set_password(password)
        user.save(using=self._db)
        return user