main.dart

// SO 29378453
import 'dart:async';

main() {
  // fails
  // main1();
  main2();
	main3();
}

// async error handling doesn't catch sync exceptions
void main1() {
  divide(1, 0).then((result) => print('(1) 1 / 0 = $result'))
    .catchError((error) => print('(1)Error occured during division: $error'));
}

Future<double> divide(int a, b) {
  // this part is still sync
  if (b == 0) {
    throw new Exception('Division by zero');
  }
  // here starts the async part
  return new Future.value(a/b);
}

// async error handling catches async exceptions
void main2() {
  divideFullAsync(1, 0).then((result) => print('(2) 1 / 0 = $result'))
      .catchError((error) => print('(2) Error occured during division: $error'));
}

Future<double> divideFullAsync(int a, b) {
  return new Future(() {
    if (b == 0) {
      throw new Exception('Division by zero');
    }
    return new Future.value(a / b);
    // or just
    // return a / b;
  });
}

// async/await allows to use try/catch for async exceptions 
main3() async {
  try {
    print('(3)');
    await divideFullAsync(1, 0);
  } catch(error){
    print('(2) Error occured during division: $error');
  }
}