field must be unique on OneToOne field in Django DRF - django

Question

I'm using Django 2.x and DRF.
I have a model to save rating for each entity
class UserRideRating(models.Model):
user_ride = models.OneToOneField(UserRide, on_delete=models.CASCADE, related_name='user_ride_rating')
rating = models.PositiveIntegerField(
validators=[validate_rating_range]
)
and serializers.py
class UserRideRatingSerializer(serializers.ModelSerializer):
class Meta:
model = UserRideRating
fields = ('id', 'user_ride', 'rating')
I have a view to create rating object if not already exists or update the rating if already exists. Also, I want to check validation using default Serializer validation and thus my view is like
#api_view(['POST'])
def rate(request):
serializer = UserRideRatingSerializer(data=request.data)
if serializer.is_valid(raise_exception=True):
# create or update data
return Response(serializer.data)
When on passing data from the postman, it gives an error as
{
"user_ride": [
"This field must be unique."
]
}
How can I enable check for only valid data and not the uniqueness of the field? Although user_ride should be unique, it can pass in the request data.

Answer 1

You have to supply the serializer with the existing instance of UserRideRating if you want to skip this unique check.
Since you are not supplying the serializer with the instance it is considering you are creating a new one with the same UserRide id.
Use this code:
#api_view(['POST'])
def rate(request):
user_ride_id = request.data.get('user_ride')
try:
instance = UserRideRating.objects.get(user_ride_id=user_ride_id)
except UserRideRating.DoesNotExist:
instance=None
serializer = UserRideRatingSerializer(instance, data=request.data)
if serializer.is_valid(raise_exception=True):
# create or update data
return Response(serializer.data)