Django DRF | Modify parent model field while creating a Child model - django

Question

I have a User model and another Admin model which has a OneToOne relationship with User model.
I am trying to modify a field in User model while an Admin model is being created.
Here is my Serializer for admin model:
class AdminSerializer(serializers.ModelSerializer):
"""A Serizlier class for vendor """
user = UserSerializer()
class Meta:
model = models.Admin
fields = ('user', 'first_name', 'last_name', 'dob', 'gender')
# This didn't work, also user_type is a field in User model and not Admin model
read_only_fields = ('user_type',)
def create(self, validated_data): # override this method <<<
"""
Since the "user" is a read_only field, the validated data doesn't contain it.
"""
# Line that causes the error. Trying to modify User model field
validated_data['user_type'] = constants.Constants.ADMIN
return super().create(validated_data)
but I get an error:
The .create() method does not support writable nested fields by
default. Write an explicit .create() method for serializer
letzbargain_api.serializers.AdminSerializer, or set read_only=True
on nested serializer fields
How can I fix this?

Answer 1

If I understand your problem correctly, you want to create Admin, but want to keep Admin's user's user_type read-only.
To do that you have to make sure user_type is read-only in your specified user serializer of AdminSerializer. For example, I am writing a new serializer:
class AdminUserSerializer(serializers.ModelSerializer):
class Meta:
model = models.User
fields = ('foo', 'bar', 'user_type')
read_only_fields = ('user_type',)
Now use that one in your AdminSerializer:
class AdminSerializer(serializers.ModelSerializer):
user = AdminUserSerializer() # make sure user_type is read-only in whatever serializer you specify here
class Meta:
model = models.Admin
fields = ('user', 'first_name', 'last_name', 'dob', 'gender')
def create(self, validated_data):
user_data = validated_data.pop('user')
user = models.User.objects.create(**user_data, user_type=constants.Constants.ADMIN)
admin = models.Admin.objects.create(user=user, **validated_data)
return admin