CODEWITHSUNDEEP
python-3.xdjango-rest-framework
Piyush
Piyush

Reputation: 599

how to check if data exist in the database in django-rest-framework

How to check if the data exist in the Database, If data not exist then it will create or else return. I have used get_or_create() but somehow i am getting the error

IntegrityError at NOT NULL constraint failed

Model Class

class UserMobileDevice(models.Model):
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE
    )
    token = models.CharField(max_length=255)
    device_model = models.CharField(max_length=255)
    os = models.CharField(max_length=255)
    os_version = models.IntegerField(null=True)
    build_version = models.CharField(max_length=255, null=True)
    manufacturer = models.CharField(max_length=255, null=True)
    device = models.CharField(max_length=255, null=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

Serializer class

class UserMobileSerializer(serializers.ModelSerializer):
    #user = serializers.StringRelatedField()
    class Meta:
        model = models.UserMobileDevice
        fields = '__all__'
        read_only_fields = ('id',)

    def create(self, validated_data):
        user, created = models.UserMobileDevice.objects.get_or_create(
            token=validated_data.get('token', None),
            defaults={'token': validated_data.get('token',None),'os':validated_data.get('os',None),'device_model':validated_data.get('device_model',None),'os_version':validated_data.get('os_version',None),'build_version':validated_data.get('build_version',None),'manufacturer':validated_data.get('manufacturer',None),'device':validated_data.get('device',None)})
        return user

View class

class UserMobileViewSet(viewsets.ModelViewSet):
    authentication_classes = (authentication.TokenAuthentication,)
    permission_classes = (permissions.IsAuthenticated,)
    queryset = UserMobileDevice.objects.all()
    serializer_class = UserMobileSerializer

    def get_queryset(self):
        return self.queryset.filter(user=self.request.user)

I am not very sure why I am getting this following error. Any help will be highly appreciated!!

Upvotes: 0

Views: 1073

Answers (2)

Aprimus
Aprimus

Reputation: 1551

You can try somethings like this in your serializer:

class UserMobileSerializer(serializers.ModelSerializer):
    #user = serializers.StringRelatedField()
    class Meta:
        model = models.UserMobileDevice
        fields = '__all__'
        read_only_fields = ('id', 'user')

    def create(self, validated_data):
        instance, created = self.Meta.model.objects.get_or_create(**validated_data)
        if not created:
            raise ValidationError('instance alreaady exists..')
        return instance

and in your view:

class UserMobileViewSet(viewsets.ModelViewSet):
    authentication_classe(authentication.TokenAuthentication,)
    permission_classes = (permissions.IsAuthenticated,)
    queryset = UserMobileDevice.objects.all()
    serializer_class = UserMobileSerializer

    def get_queryset(self):
        return self.queryset.filter(user=self.request.user)

    def perform_create(self, serializer):
        user = self.request.user
        serializer.save(user=user)

Upvotes: 1

Ayush Pallav
Ayush Pallav

Reputation: 1057

You are getting constraint error because the fields have been defined not to be null and you might be populating a null value in it.

There are two major issues here:

  1. User is a foreign key to AUTH_USER_MODEL, but no instance for the same is created when you are populating using get_or_create. Based on the code snippets you shared, you dont actually need to have a foreign key to user model, instead you can just extend the user model.

        from django.contrib.auth.models import User

    class UserMobileDevice(User):
        # Your code

  2. Secondly, your model defines fields like token etc as Non null-able fields. So, using None to populate data makes no sense.

Upvotes: 0

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