Dart by Example: Exceptions

  1. //
  2. class FoodSpoiledError extends StateError {
  3.   FoodSpoiledError(String msg) : super(msg);
  4. }
  6. class Potato {
  7.   int age;
  9.   Potato(this.age);
  11.   String peel() {
  12.     if (age > 4) {
  13.       throw new FoodSpoiledError('your potato is spoiled');
  14.     }
  15.     return "peeled";
  16.   }
  17. }
  19. main() {
  20.   var p = new Potato(7);
  22.   try {
  23.     p.peel();
  24.   } on FoodSpoiledError catch(_) {
  25.     print("nope nope nope");
  26.   }
  28.   // any non-null object can be thrown:
  29.   try {
  30.     throw("potato");
  31.   } catch(_) {
  32.     print("caught a flying potato");
  33.   }
  35.   // exceptions halt excecution
  36.   p.peel();
  37.   print('not reached');
  38. }
  39.  
  1. $ dart exceptions.dart
  2. nope nope nope
  3. caught a flying potato
  4. Unhandled exception:
  5. Bad state: your potato is spoiled
  6. #0      Potato.peel (file:///exceptions.dart:13:7)
  7. #1      main (file:///exceptions.dart:36:5)
  8. #2      _startIsolate.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:261)
  9. #3      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:148)

by @jryanio | source | license