How to update OneToOneField using Django Rest Framework - django

Question

I'm trying to make an image upload through a REST API from a mobile client. I've managed to implement it using an multipart request to the REST endpoint, but when I try to update the image, the request is not handled correctly because of the constraints on the OneToOneField.
This is how I implemented the API:
models.py
class Hotel(models.Model):
name = models.CharField(max_length=500, null=False, blank=False)
address = models.CharField(max_length=500, null=False, blank=False)
rating = models.FloatField()
owner = models.CharField(max_length=200, null=False)
class Meta:
ordering = ['name']
class HotelPhoto(models.Model):
photo = models.ImageField(upload_to='hotel_photos', null=True)
hotel = models.OneToOneField(Hotel, on_delete=models.CASCADE, primary_key=True)
views.py
class HotelPhotoUpload(APIView):
parser_classes = [FormParser, MultiPartParser]
def post(self, request):
photo_serializer = HotelPhotoSerializer(data=request.data,
context={'request': request})
if photo_serializer.is_valid():
photo_serializer.save()
return Response(photo_serializer.data,
status=status.HTTP_201_CREATED)
else:
logger.error(f'Error uploading image: {photo_serializer.errors}')
return Response(photo_serializer.errors,
status=status.HTTP_400_BAD_REQUEST)
serializers.py
class HotelSerializer(serializers.HyperlinkedModelSerializer):
photo = serializers.ImageField(source='hotelphoto.photo', read_only=True)
class Meta:
model = Hotel
fields = ['url', 'id', 'name', 'address', 'rating', 'owner', 'photo']
class HotelPhotoSerializer(serializers.ModelSerializer):
photo_url = serializers.SerializerMethodField()
class Meta:
model = HotelPhoto
fields = ['hotel', 'photo', 'photo_url']
def get_photo_url(self, obj):
return self.context['request'].build_absolute_uri(obj.photo.url)
This is the error I'm getting:
Error uploading image: {'hotel': [ErrorDetail(string='hotel photo with this hotel already exists.', code='unique')]}
Bad Request: /hotels/photo/upload/
I understand this is due to the constraint on the OneToOneField since I've have already uploaded a photo, but how should I do the request in order to just update the HotelPhoto.photo field?
What I've tried
Implementing a put method on the HotelPhotoUpload view with partial=True on the serializer, but it gave the same error.
I thought about overwriting the validate method on the serializer, but I don't know if I need to validate anything on the photo itself. I was hoping the framework would handle this for me.
Thought about merging the HotelPhoto and Hotel models, but that would require a big refactor of other code.
EDIT:
I'm currently using django 3.0.2.
Following the answer by neferpitou, I've managed to get it working after these minor changes:
serializers.py
# Didn't change the HotelSerializer
class HotelPhotoSerializer(serializers.ModelSerializer):
hotel = serializers.PrimaryKeyRelatedField(
many=False,
queryset=Hotel.objects.all())
class Meta:
model = HotelPhoto
fields = ['hotel', 'photo']
def create(self, validated_data):
# Instead of creating a new HotelPhoto instance
# changed the photo field from the Hotel instance
hotel = validated_data.get('hotel')
photo = validated_data.get('photo')
hotel.hotelphoto.photo.save(photo.name, photo)
hotel.save()
return hotel.hotelphoto
views.py
class HotelPhotoUpload(APIView):
parser_classes = [FormParser, MultiPartParser]
def post(self, request):
# I'm already sending the hotel id on the POST request
photo_serializer = HotelPhotoSerializer(data=request.data)
if photo_serializer.is_valid():
photo_serializer.save()
return Response(photo_serializer.data,
status=status.HTTP_201_CREATED)
else:
logger.error(f'Error uploading image: {photo_serializer.errors}')
return Response(photo_serializer.errors,
status=status.HTTP_400_BAD_REQUEST)
One thing that I forgot to mention is that I'm always sending a request (either POST or PUT) to the hotels endpoint (which uses the HotelSerializer) before uploading a photo. So I'm not expecting to have problems on the photo/upload endpoint due to an inexistent hotel.
mobile client
Unfortunaly can't post the Multipart POST request content because it's huge. But here is the client method implementation using Retrofit 2.5.0.
// Sends the hotel id and the entire content of the photo file.
#Multipart
#POST(UPLOAD_ENDPOINT)
fun uploadPhoto(#Part("hotel") hotelId: RequestBody,
#Part photo: MultipartBody.Part) : Call<UploadResult>
companion object {
const val UPLOAD_ENDPOINT = "hotels/photo/upload/"
}

Answer 1

Foreignkey and OneToOneField can be serialized in the same manner.
Here is your
views.py
class HotelPhotoUpload(APIView):
# parser_classes = [FormParser, MultiPartParser]
def post(self, request):
hotel = Hotel.objects.get(name=request.data.get('hotel'))
request.data['hotel'] = hotel.id
photo_serializer = HotelPhotoSerializer(data=request.data)
# print(photo_serializer)
if photo_serializer.is_valid():
photo_serializer.save()
return Response(photo_serializer.data,
status=status.HTTP_201_CREATED)
else:
# logger.error(f'Error uploading image: {photo_serializer.errors}')
return Response(photo_serializer.errors,
status=status.HTTP_400_BAD_REQUEST)
serializers.py
class HotelSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Hotel
fields = '__all__'
class HotelPhotoSerializer(serializers.ModelSerializer):
hotel = serializers.PrimaryKeyRelatedField(many=False, queryset=Hotel.objects.all())
class Meta:
model = HotelPhoto
fields = ['hotel', 'photo',]
def create(self, validated_data):
hotel_photo = HotelPhoto.objects.create(**validated_data)
hotel_photo.save()
return hotel_photo
I am confused why there are extra fields in your HotelSerializer, so I have trimmed it down. If you have specific use case for those feel free to modify in your code. And there are no primary key in your Hotel model, so it will create id field by default and I am assuming every hotel name in unique.
Postman request:
Hotel Data From Admin Section: