Wsrtjtyk

I'm building a simple budgeting app to work on learning Django & React. I've used DRF to build an API to create and get transactions from the database. I'm currently calculating the total running balance on the fly when I do my GET. This has been working well, but when I do a POST I get an error that my dynamic balance field is required since that field is in my serializer. How can I get around this?

views.py

class CreateView(generics.ListCreateAPIView):

    """This class defines the GET & POST behavior of the rest api."""



    queryset = Transaction.objects.all()



    # This is the balance that's calculated on the fly

    queryset_with_balance = queryset.annotate(balance=Window(Sum('amount'),

                                                             order_by=F('created_time').asc())).all().order_by('-created_time')



    serializer_class = TransactionSerializer



    def perform_create(self, serializer):

        """Save the post data when creating a new transaction."""

        serializer.save()



    def get_queryset(self):

        return self.queryset_with_balance

serializers.py

class TransactionSerializer(serializers.ModelSerializer):

    balance = serializers.DecimalField(decimal_places=2, max_digits=19)



    class Meta:

        """Meta class to map serializer's fields with the model fields."""

        model = Transaction

        fields = ('id', 'date', 'payee', 'category',

                  'amount', 'balance', 'created_time', 'modified_time')

models.py

class Transaction(models.Model):

    date = models.DateField()

    payee = models.CharField(max_length=256)

    category = models.CharField(max_length=256)

    amount = MoneyField(max_digits=19,

                        decimal_places=2,

                        default_currency='USD')    

    created_time = models.DateTimeField(auto_now_add=True)

    modified_time = models.DateTimeField(auto_now=True)

set balance field as read_only as below,

class TransactionSerializer(serializers.ModelSerializer):

    balance = serializers.DecimalField(decimal_places=2, max_digits=19, read_only=True)

    # your code

From the DRF doc

Read-only fields are included in the API output, but should not be included in the input during create or update operations.