How to save a modelSerializer that has relations? - django - django

Question

I want to save a sent json data to db by django-rest-framework.
the problem is, not saving the relation and returns error.
The bellow snippet is my models:
class Profile(models.Model):
user = models.OneToOneField(settings.AUTH_USER_MODEL, related_name='profile', on_delete=models.CASCADE)
name = models.CharField(max_length=30)
family = models.CharField(max_length=50)
class Klass(models.Model):
title = models.CharField(max_length=50)
description = models.CharField(max_length=500)
teacher = models.ForeignKey(Profile, related_name='teacher', on_delete=models.CASCADE)
I use below serializer for serializing/deserializing the Klass model.
class ProfileSerializer(serializers.ModelSerializer):
class Meta:
model = Profile
fields = ('pk', 'name', 'family')
class KlassSerializer(serializers.ModelSerializer):
teacher = ProfileSerializer()
class Meta:
model = Klass
fields = ('id', 'title', 'description', 'teacher')
now when I prepare a JSON object and send it to the view, it returns error. the below is the view class:
class KlassView(APIView):
"""for SELECT, INSERT Queries"""
def get(self, request, pk):
# somthing
#csrf_exempt
def post(self,request, pk=None):
"""For Creating A Class"""
serializer = KlassSerializer(data=request.data)
if serializer.is_valid():
teacher = ProfileSerializer(request.data['teacher']['pk'])
serializer.teacher = teacher.data
serializer.save()
return Response({'data': serializer.data})
else:
return Response({'data': serializer.errors})
and the error is:
The .create() method does not support writable nested fields by default.
Write an explicit .create() method for serializer mainp.serializers.KlassSerializer, or set read_only=True on nested serializer fields.
How can I save relation in KlassSerializer in order to save to db?

Answer 1

At first change your serializer like below:
class KlassSerializer(serializers.ModelSerializer):
# teacher = ProfileSerializer() # No need to this!
class Meta:
model = Klass
# fields = ('id', 'title', 'description', 'teacher')
fields = ('id', 'title', 'description') # Omit teacher
Then get profile from requested user and pass it to your serializer:
def post(self,request, pk=None):
"""For Creating A Class"""
serializer = KlassSerializer(data=request.data)
if serializer.is_valid():
teacher = ProfileSerializer(request.data['teacher']['pk'])
serializer.teacher = teacher.data
serializer.save(teacher=request.user.profile) # Retrieve teacher and stroe
return Response({'data': serializer.data})
else:
return Response({'data': serializer.errors})

Answer 2

Just override the create method of ModelSerializer in KlassSerializer.
class KlassSerializer(serializers.ModelSerializer):
teacher = ProfileSerializer()
class Meta:
model = Klass
fields = ('id', 'title', 'description', 'teacher')
def create(self, validated_data):
profile = Profile.objects.filter(pk=validated_data['teacher']['pk'])
if profile:
k = Klass()
k.teacher = profile
...