AttributeError в Сериализаторе Джанго

Question

Я занимаюсь разработкой приложения, и одна из его функций заключается в том, что оно может распознавать устройство, но иногда оно ничего не возвращает. Это может быть ошибка API, который я использую.

Модель устройства следующая:

class Device(models.Model):
"""

"""
user = models.ForeignKey(get_user_model(), on_delete=models.CASCADE)
deviceModel = models.CharField(max_length=128, verbose_name=_(u"Device Model"))
deviceId = models.CharField(max_length=128, verbose_name=_(u"Device ID"))
packageId = models.CharField(max_length=128, verbose_name=_(u"Package ID"))
tokenId = models.TextField(verbose_name=_(u"Token ID"))
platformId = models.CharField(max_length=10, verbose_name=_(u"Plataforma ID"))
created_at = models.DateTimeField(auto_now=True, verbose_name=_(u"Created"))
updated_at = models.DateTimeField(auto_now=True, verbose_name=_(u"Updated"))

def __str__(self):
    return u'Device: {0}'.format(self.deviceId)

def __unicode__(self):
    return self.__str__()

def send_logout(self):
    """
    Send logout Notification Message
    """
    active_session = ActiveSession.objects.filter(
        device=self
    ).first()

    if active_session:
        push_service = FCMNotification(api_key=settings.FCM_API_KEY)
        data_message = {
            "action": "Logout",
            "token_id": active_session.token_jwt
        }
        push_service.single_device_data_message(
            registration_id=self.tokenId,
            data_message=data_message,
            content_available=True
        )

И сериализатор:

class DeviceSerializer(ModelSerializer):
def create(self, validated_data):
    # Check if exist
    device = Device.objects.filter(user=validated_data["user"], deviceId=validated_data['deviceId']).first()
    today = timezone.now()

    # If exist, update
    if device:
        device.tokenId = validated_data['tokenId']
        device.updated_at = today
        device.save()
        logger.info("[Device] Updated deviceID {} with token {} for user {}".format(
            validated_data['deviceId'],
            validated_data['tokenId'],
            validated_data["user"].username
        ))
    else:
        device = Device(**validated_data)
        device.save()
        logger.info("[Device] Created deviceID {} with token {} for user {}".format(
            validated_data['deviceId'],
            validated_data['tokenId'],
            validated_data["user"].username
        ))

    # Associate Device to ActiveSession
    active_session = ActiveSession.get_active_session(self.context.get('request'))
    active_session.device = device
    active_session.save()

    return device

class Meta:
    model = Device
    fields = ("id", "deviceModel", "deviceId", "packageId", "tokenId", "platformId")

Ошибка, которую я получаю из этой строки active_session.device = device

Я хочу столкнуться с этой ошибкой, создав исключение для этого AttributeError. Но мой разум открыт для идей.

Полный возврат:

[ERROR] 15:12 Internal Server Error: /api/device/
Traceback (most recent call last):
  File "/home/user/.local/lib/python2.7/site-packages/django/core/handlers/exception.py", line 39, in inner
    response = get_response(request)
  File "/home/user/.local/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/user/.local/lib/python2.7/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/user/.local/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
  File "/home/user/.local/lib/python2.7/site-packages/rest_framework/viewsets.py", line 103, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/user/.local/lib/python2.7/site-packages/rest_framework/views.py", line 483, in dispatch
    response = self.handle_exception(exc)
  File "/home/user/.local/lib/python2.7/site-packages/rest_framework/views.py", line 443, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/home/user/.local/lib/python2.7/site-packages/rest_framework/views.py", line 480, in dispatch
    response = handler(request, *args, **kwargs)
  File "/home/user/Downloads/ID/id/modules/api/views.py", line 69, in create
    self.perform_create(serializer)
  File "/home/user/Downloads/ID/id/modules/api/views.py", line 78, in perform_create
    serializer.save(user=self.request.user)
  File "/home/user/.local/lib/python2.7/site-packages/rest_framework/serializers.py", line 214, in save
    self.instance = self.create(validated_data)
  File "/home/user/Downloads/ID/id/modules/api/serializers.py", line 65, in create
    active_session.device_test = device
AttributeError: 'NoneType' object has no attribute 'device_test'

Answer 1

Ошибка AttributeError может происходить во многих случаях, но часто случается, если попытаться выполнить неправильную связь со связанной моделью. В этом случае, если ваш ActionveSessionModel имеет другое имя related_name для «устройство», «устройство» не будет найдено.

https://docs.djangoproject.com/en/2.2/topics/db/models/#be-careful-with-related-name-and-related-query-name

https://github.com/django/django/blob/master/django/db/models/fields/related_descriptors.py#L98