Django rest nested serializer fails - django

Question

My model relationships are: A 'Reader' will have a single 'Wishlist' and a 'Wishlist' will contain many 'Book's. I want to create an empty Wishlist automatically during Reader object instance creation.
My Models:
class Wishlist(models.Model):
wishlist_id = models.AutoField(primary_key=True)
class Reader(models.Model):
user = models.OneToOneField(User)
phone = models.CharField(max_length=30)
address = models.CharField(max_length=80)
dob = models.DateField(auto_now=False, auto_now_add=False, null=True, blank=True)
# A library has many readers
which_library = models.ForeignKey('Library', related_name='readers', on_delete=models.CASCADE)
wishlist = models.OneToOneField(Wishlist, null=True, blank=True)
class Book(models.Model):
book_id = models.AutoField(primary_key=True)
title = models.CharField(max_length=30)
which_wishlist = models.ForeignKey('Wishlist', related_name='my_wishlist', on_delete=models.CASCADE, null=True, blank=True)
And serializer:
class ReaderSerializer(serializers.ModelSerializer):
username = serializers.CharField(source='user.username')
email = serializers.CharField(source='user.email')
password = serializers.CharField(source='user.password')
class Meta:
model = Reader
#fields = '__all__'
#depth = 1
fields = ('id', 'username', 'email', 'password', 'phone', 'address', 'dob', 'which_library', 'wishlist')
def update(self, instance, validated_data):
instance.user.email = validated_data.get('user.email', instance.user.email)
instance.user.password = validated_data.get('user.password', instance.user.password)
instance.phone = validated_data.get('phone', instance.phone)
instance.address = validated_data.get('address', instance.address)
instance.dob = validated_data.get('dob', instance.dob)
instance.which_library = validated_data.get('which_library', instance.which_library)
instance.wishlist = validated_data.get('wishlist', instance.wishlist)
instance.save()
return instance
def create(self, validated_data):
user_data = validated_data.pop('user')
user = User.objects.create(**user_data)
user.set_password(user_data['password'])
user.save()
wishlist_data = validated_data.pop('wishlist')
reader = Reader.objects.create(**validated_data)
Wishlist.objects.create(reader=reader, **wishlist_data)
return reader
My view that handles the creation:
#api_view(['GET', 'POST'])
def reader(request, library_id):
"""
List all readers in a specific library, or create a new
"""
if request.method == 'GET':
...
elif request.method == 'POST':
serializer = ReaderSerializer(data=request.data)
if serializer.is_valid():
serializer.save()
return Response(serializer.data, status=status.HTTP_201_CREATED)
else:
return Response(
serializer.errors, status=status.HTTP_400_BAD_REQUEST)
I am making a POST call to create a Reader with following JSON data:
{
"username": "sample",
"email": "sample#gmail.com",
"password": "012345",
"phone": "012345",
"address": "sample address",
"which_library": "2",
"wishlist": []
}
Where it gives me following error:
{
"wishlist": [
"Incorrect type. Expected pk value, received list."
]
}
What am I doing wrong?

Answer 1

I would throw away the Wishlist model completely as it does not hold any data.
class Book(models.Model):
book_id = models.AutoField(primary_key=True)
title = models.CharField(max_length=30)
reader = models.ManyToManyField('Reader', related_name='wishlist')
This should make the whole thing easier as you no longer need to create the wishlist automagically and I guess your problem will desolve in air.
If you need the Model (e.g. you expect data to arise later) you might use through on the ManyToManyField. Details can be found in the docs
UPDATE
I rethought the advise regarding the through model. This approach would not reflect your current state as it would have one entry per relation not per reader. Nevertheless I would recommend the simplification of your models as suggested above.