• Exception
• Error

• 还有些子类

• dart 可以抛出任意非 null 对象

Throw

throw FormatException('Expected at least 1 section');

• 抛出任意对象

throw 'Out of llamas!';

• =>

void distanceTo(Point other) => throw UnimplementedError();

Catch

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

• 处理异常

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');
}

• catch 可以接受两个对象
  • 异常对象
  • stack trace

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

• 处理异常后还可抛出

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

• 异常没有被捕捉, 那么异常在 finally 之后再传播

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

• finally 在异常被捕获后运行

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