Update data using RetrieveUpdateAPIView - Getting validated data from a serializer - django

Question

I would like to update certain properties of a user (say first_name and last_name)
my json object through a PUT request would look like this
{
"user" : {
"first_name": "Jack",
"last_name": "shnider",
"password":"admin123"
"email" : "foo#google.com"
},
"employee_zip" : 12345
}
This is what my view looks like (I would like to update the existing fields to these new fields).
These are the serializer
class Serializer_UpdateUser(ModelSerializer):
class Meta:
model = User
fields = ('first_name','last_name','password')
class Serializer_UpdateEmployer(ModelSerializer):
user = Serializer_UpdateUser()
class Meta:
model = modelEmployer
fields = [
'user',
'employer_zip',
]
This is the view :
class UpdateProfile_RetrieveUpdateAPIView(RetrieveUpdateAPIView):
queryset = modelEmployer.objects.all()
serializer_class = Serializer_UpdateEmployer
lookup_field = 'user__email'
permission_classes = [permissions.AllowAny]
def update(self, request, *args, **kwargs):
instance = self.get_object() #------>I have the object that I would like to update
serializer = self.get_serializer(instance, data=request.data, partial=partial)
serializer.is_valid(raise_exception=True) #--->Success
Now I would like to get a validated fields (The json only contains the fields that have been updated). I know if I do something like this
serializer.save
I would get back a modelEmployer but instead I get back this error
AssertionError at /api/employer/update_profile/employerA#gmail.com/ The `.update()` method does not support writable nested fields by default. Write an explicit `.update()` method for serializer `Employer.api.serializers.Serializer_ListEmployer`, or set `read_only=True` on nested serializer fields. Request Method:
I have two questions
1-Why is save failing ?
2-How can I get the validated data from the above serializer ?

Answer 1

The save is failing because django-rest-framework doesn't deal with nested serializers by default.
from the django-rest-framework docs:
By default nested serializers are
read-only. If you want to support write-operations to a nested
serializer field you'll need to create create() and/or update()
methods in order to explicitly specify how the child relationships
should be saved.
You have to override the update method in the serializer to allow that behavior:
class Serializer_UpdateEmployer(ModelSerializer):
user = Serializer_UpdateUser()
class Meta:
model = modelEmployer
fields = [
'user',
'employer_zip',
]
def update(self, instance, validated_data):
user_data = validated_data.pop('user', {})
user_serializer = Serializer_UpdateUser(instance.user, data=user_data)
user_serializer.save()
return instance
Another solution is to use drf-writable-nested. It automatically makes your nested serializers updatable.
from drf_writable_nested import WritableNestedModelSerializer
class Serializer_UpdateEmployer(WritableNestedModelSerializer):
user = Serializer_UpdateUser()
class Meta:
model = modelEmployer
fields = [
'user',
'employer_zip',
]

Answer 2

I think drf-writable-nested can help you to update nested data.
In you case:
from django.contrib.auth import password_validation
class Serializer_UpdateUser(ModelSerializer):
def update(self, instance, validated_data):
password = validated_data.pop('password', None)
super(Serializer_UpdateUser, self).update(instance, validated_data)
if password is not None:
instance.set_password(password)
instance.save()
return instance
def validate_password(self, value):
password_validation.validate_password(value)
return value
class Meta:
model = User
fields = ('first_name','last_name','password')
class Serializer_UpdateEmployer(WritableNestedModelSerializer):
user = Serializer_UpdateUser()
class Meta:
model = modelEmployer
fields = [
'user',
'employer_zip',
]
Note you need special handling password field.