Error after overriding create method in serializer - django

Question

I'm Overriding create method of serializer in order to manipulate validated_data and create object in a model, Although it works, in the end I get below error, i am not able to figure out why after lot of research.
AttributeError: Got AttributeError when attempting to get a value for field `shift_time` on serializer `PunchRawDataAndroidSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `PunchRawData` instance.
Original exception text was: 'PunchRawData' object has no attribute 'shift_time'.
class PunchRawDataAndroidSerializer(serializers.ModelSerializer):
employee_id = serializers.CharField()
shift_id = serializers.CharField()
work_location_id = serializers.CharField()
shift_time = serializers.TimeField()
class Meta:
model = PunchRawData
fields = ['employee_id', 'shift_id','work_location_id', 'punch_type', 'actual_clock_datetime',
'emp_photo', 'created_at', 'updated_at','shift_time']
def create(self, validated_data):
validated_data.pop('shift_time')
request_data = self.context.get('request')
user = request_data.user
validated_data['user'] = user
data = validated_data
return PunchRawData.objects.create(**data)
class PunchRawDataAndroidViewSet(viewsets.ModelViewSet):
serializer_class = PunchRawDataAndroidSerializer
parser_classes = (MultiPartParser, FileUploadParser)
edit:
class PunchRawData(models.Model):
PUNCH_TYPES = [("in", "Punch IN"), ("out", "Punch Out")]
employee = models.ForeignKey(Employee, related_name="punch_employee", on_delete=models.CASCADE)
shift = models.ForeignKey(WorkShift, on_delete=models.CASCADE)
work_location = models.ForeignKey(HRMLocation, blank=True, on_delete=models.CASCADE,
null=True, related_name="punch_work_location")
punch_type = models.CharField(max_length=255, null=True, blank=True, choices=PUNCH_TYPES)
user = models.ForeignKey("useraccounts.User", on_delete=models.CASCADE)
actual_clock_datetime = models.DateTimeField(null=True, blank=True)
emp_photo = models.ImageField(upload_to="selfies/%Y/%m/%d/%I/%M/%S/")
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
def __str__(self):
strl = "{emp_id} [{shift_id}]".format(emp_id=self.employee.emp_id,
shift_id=self.shift.shift_id)
return strl
class Meta:
verbose_name = "Punch Raw Data"
verbose_name_plural = "Punch Raw Data"
I get shift_time from frontend and it is not from model, hence i'm poping it out from validated_data in create method. is error related to modelviewset?

Answer 1

Your model doesn't have the shift_time attribute. So if you try to save it, you will end with
PunchRawData() got an unexpected keyword argument 'shift_time'
At the other hand you are getting AttributeError, because serializers.to_representation() tries to get a non-existing attribute when showing your freshly saved object.
If this should be a read-only attribute, you may do the following:
shift_time = serializers.TimeField(read_only=True)
and than remove the
validated_data.pop('shift_time')
from PunchRawDataAndroidSerializer.create(). You don't need this any more, because it is never submitted from your client.
If you need the opposite – your client should provide you that field, but you don't want it saved in your model, than the only thing, you should do, is:
shift_time = serializers.TimeField(write_only=True)
And if you need it to be bidirectional, than you should add it to your model.
Hope this helps.

Answer 2

Adding to #wankata's answer we can override __init__ method to have write_only field for only create method.
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
if self.context['view'].action == 'create':
self.fields['shift_time'].write_only = True

Answer 3

Generic viewsets of django-rest-framework return the serialized representation of the model in response, so it's try to serialize the model including the shift_time key.
To avoid this problem you can specify the shift_time field as write_only. documentation
modify the Meta class on your model
class Meta:
model = PunchRawData
fields = ['employee_id', 'shift_id','work_location_id', 'punch_type', 'actual_clock_datetime',
'emp_photo', 'created_at', 'updated_at','shift_time']
extra_kwargs = {'shift_time': {'write_only': True}}