Use value of related field when saving/POST django-rest-framework - django

Question

Im trying to find a method for posting a string value and saving it to a foreign key field instead of using the pk.
My models:
class CustomUser(models.Model):
username = models.CharField(max_length=500, unique=True)
def __str__(self):
return self.username
class Order(models.Model):
ordernumber = models.UUIDField(primary_key=False, default=uuid.uuid4, editable=False)
user = models.ForeignKey(CustomUser, on_delete=models.SET_NULL, null=True, blank=True)
amount = models.FloatField(null=True, blank=True)
def __str__(self):
return "{0}".format(self.ordernumber)
And my serializer:
class OrderSerializer(serializers.ModelSerializer):
username = serializers.CharField(source='user.username')
class Meta:
model = Order
fields = ('id','username', 'ordernumber', 'amount')
read_only_fields = ('id')
When using GET, everything works perfectly, but I can't seem to fix the POST method.
I tried to override the create method like this:
def create(self, validated_data):
username = validated_data.pop('username')
order = Order.objects.create(**validated_data)
order.user = CustomUser.objects.get(username=username)
order.save()
return order
But I get a KeyError on the username = validated_data.pop('username') line: Exception Value:'username'

Answer 1

When you use source with nested fields, data will be accessible as validated_data['parent_field']['child_field']. Try this:
def create(self, validated_data):
user_data = validated_data.pop('user')
username = user_data.pop('username')
order = Order.objects.create(**validated_data)
order.user = CustomUser.objects.get(username=username)
order.save()
return order