Solution: Example problem needing FutureOr<> in Dart

main.dart

import 'dart:async';

String callbackOne() => "hello";

Future<String> callbackTwo() async => (await Future.delayed(Duration(seconds: 1),() => "This is a sentence"));

Future<int> getLengthOfResult(FutureOr<String> Function() callback) async {
  // I can await on callbackOne, even though it returns a String.
  final result = await callback();
  return result.length;
}

Future<int> getLengthOfResult2(String Function() callback) async {
  return callback().length;
}

main() async {
  print("Length of callbackOne result: ${await getLengthOfResult(callbackOne)}");
    print("Length of callbackTwo result: ${await getLengthOfResult(callbackTwo)}");
}

// Solution for https://dartpad.dev/?id=0e12aa0f4745213a7efa5b5ff8c4934e