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Use AsyncValue.guard rather than try/catch inside your StateNotifier subclasses

When writing your own StateNotifier subclasses, it's quite common to use try/catch blocks to deal with Futures that can fail:

class SignOutButtonController extends StateNotifier<AsyncValue> { SignOutButtonController({required this.authRepository}) : super(const AsyncValue.data(null)); final AuthRepository authRepository; Future<void> signOut() async { try { state = const AsyncValue.loading(); await authRepository.signOut(); // this future can fail state = const AsyncValue.data(null); } catch (e) { state = AsyncValue.error(e); } } }

In such cases, AsyncValue.guard is a convenient alternative that does all the heavy-lifting for us:

Future<void> signOut() async { state = const AsyncValue.loading(); state = await AsyncValue.guard(() => authRepository.signOut()); }

Here's how this method is implemented in the the AsyncValue class:

abstract class AsyncValue<T> { static Future<AsyncValue<T>> guard<T>(Future<T> Function() future) async { try { return AsyncValue.data(await future()); } catch (err, stack) { return AsyncValue.error(err, stackTrace: stack); } } }

Learn more here: AsyncValue.guard() method.

Happy coding!

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