Exceptions processing in regular+future case

mafia_risky_job.dart

import 'dart:math';

class PoliceException implements Exception {
  PoliceException({this.msg});

  final String msg;

  @override
  String toString() => 'Police Raid {$msg}';
}

class RiskyDealer {
  RiskyDealer(this.name);

  final String name;

  Future<String> dangerMove() async {
    print('$name start hustle');

    await Future.delayed(Duration(seconds: 1));

    var rng = new Random();
    if (rng.nextInt(4) == 0) {
      throw PoliceException(msg: 'Dealer <$name> arrested');
    }

    if (rng.nextInt(3) == 0) {
      return Future.error('$name was ripped of');
    }

    return '$name pushed some stuff';
  }
}

void main() async {
  List<RiskyDealer> mafia = [
    RiskyDealer('[1]Rob'),
    RiskyDealer('[2]Mike'),
    RiskyDealer('[3]Carlos'),
    RiskyDealer('[4]Walter'),
    RiskyDealer('[5]Jesse'),
    RiskyDealer('[6]Gomez'),
    RiskyDealer('[7]Daniel'),
  ];

  print('>>>Mafia starts deals\n');

  try {
    for (RiskyDealer dealer in mafia) {
      await dealer
          .dangerMove()
          .then((result) => print('SUCCESS: $result'))
          .catchError((fail) {
        if (fail is PoliceException) {
          print('FIASCO!!!');
          throw fail;
        }
        print('FAILED: $fail');
      });
      await Future.delayed(Duration(seconds: 1), () => print('\n>next turn<'));
    }
  } on PoliceException catch (alarm) {
    print(alarm);
    print('\n>>>Mafia was unveiled!');
    return;
  }
  
  print('\n>>>Mafia survives!');
}

Try in DartPad
https://dartpad.dartlang.org/8fa6b271bc3fe178018d58b144da3bec