Dart : Exceptions

Dart Exceptions

Dart Exceptions

Throw

throw FormatException('Expected at least 1 section');
// throw arbitarary objects
throw 'Out of llamas!';
void distanceTo(Point other) => throw UnimplementedError();

Catch

try {
  breedMoreLlamas();
} on OutOfLlamasException {
  buyMoreLlamas();
}

// multiple catch clauses
try {
  breedMoreLlamas();
} on OutOfLlamasException {
  // A specific exception
  buyMoreLlamas();
} on Exception catch (e) {
  // Anything else that is an exception
  print('Unknown exception: $e');
} catch (e) {
  // No specified type, handles all
  print('Something really unknown: $e');
}

// one or two parameters
try {
  // ···
} on Exception catch (e) {
  print('Exception details:\n $e');
} catch (e, s) {
  print('Exception details:\n $e');
  print('Stack trace:\n $s');
}

// rethrow to caller
void misbehave() {
  try {
    dynamic foo = true;
    print(foo++); // Runtime error
  } catch (e) {
    print('misbehave() partially handled ${e.runtimeType}.');
    rethrow; // Allow callers to see the exception.
  }
}

void main() {
  try {
    misbehave();
  } catch (e) {
    print('main() finished handling ${e.runtimeType}.');
  }
}

Finally

try {
  breedMoreLlamas();
} finally {
  // Always clean up, even if an exception is thrown.
  cleanLlamaStalls();
}

try {
  breedMoreLlamas();
} catch (e) {
  print('Error: $e'); // Handle the exception first.
} finally {
  cleanLlamaStalls(); // Then clean up.
}

library Error and Exception

Exception class

• DeferredLoadException
• FormatException
• IntegerDivisionByZeroException
• IOException
• IsolateSpawnException
• TimeoutException

Error class

• AbstractClassInstantiationError
• ArgumentError
• AssertionError
• AsyncError
• CastError
• ConcurrentModificationError
• CyclicInitializationError
• FallThroughError
• JsonUnsupportedObjectError
• NoSuchMethodError
• NullThrownError
• OutOfMemoryError
• RemoteError
• StackOverflowError
• StateError
• UnimplementedError
• UnsupportedError