Django Rest Framework Serializer not printing nested relationship - django

Question

I've got established a relationship between 2 models: Order and OrderLine. I've created serializers for both of them following the DRF documentation, yet when printing the serializer.data the nested objects don't show.
Here are my models:
class Order(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
session_id = models.CharField(max_length=256)
class OrderLine(models.Model):
order_id = models.ForeignKey(Order, on_delete=models.DO_NOTHING)
product_id = models.ForeignKey(Product, on_delete=models.DO_NOTHING)
price = models.DecimalField(decimal_places=2, max_digits=20)
quantity = models.IntegerField()
total = models.DecimalField(decimal_places=2, max_digits=20)
created_at = models.DateField(auto_now_add=True)
updated_at = models.DateField(auto_now=True)
These are the serializers:
from rest_framework import serializers
from .models import Order, OrderLine
class OrderLineSerializer(serializers.ModelSerializer):
"""
OrderLine serializer
"""
class Meta:
model = OrderLine
fields = ['product_id', 'price', 'quantity', 'total']
class OrderSerializer(serializers.ModelSerializer):
"""
Order serializer
"""
items = OrderLineSerializer(many=True, read_only=True)
class Meta:
model = Order
fields = ['session_id', 'subtotal', 'total', 'items']
read_only_fields = ['id']
and this is the view:
class OrderAPIViewSet(viewsets.ViewSet):
def create(self, request):
order = Order.objects.create(session_id=request.data['session_id'])
for item in request.data['items']:
product = Product.objects.get(pk=item['product_id'])
total = Decimal(item['price'] * item['quantity'])
OrderLine.objects.create(
order_id=order,
product_id=product,
price=Decimal(item['price']),
quantity=item['quantity'],
total=total
)
serializer = OrderSerializer(instance=order)
print("HERE")
print(serializer.data)
return Response(status=status.HTTP_200_OK)
From my REST client I'm posting the following object:
{
"session_id":uuid,
"items": [
{
"product_id": product.id,
"price": 5.80,
"quantity": 2,
}
]
}
but when the print statement in the view is executed this is what's being printed:
{
"session_id":"4def7bdb-dedb-46aa-9c70-1d9e4f522149",
"subtotal":"0.00",
"total":"0.00"
}
notice the the items subresource is not being included.
What am i missing?

Answer 1

Because you passed read_only=True parameter to OrderLineSerializer. When your serializer's builtin method to_internal_value() run, clear data not including in your fields list. For more details: read_only