Why cant I use .sum in a Stateful Widget?

Why cant I use .sum in a Stateful Widget?

Problem Description:

I have built out a stateless widget that I now need to change to a stateful widget. Within my stateless widget, I have a function…

            SumOfRoundedTankValue() {
              List<double> numbers = [];
                port.ports.tankSpecs.forEach((e) {
                  numbers.add(double.parse(e.defUsGallons));
              });
                final sum = numbers.sum;
                return (sum);
            }

Why does this function not work in a stateful widget? I get the squiggly line under .sum that says:

The getter ‘sum’ isn’t defined for the type ‘List’.
Try importing the library that defines ‘sum’, correcting the name to the name of an existing getter, or defining a getter or field named ‘sum’.

Solution – 1

This is not issue of Statless or Statefull widgets

Just import to your dart file

import 'package:collection/collection.dart';

After that sum property will be available to your Iterable

final sum = numbers.sum;