useGuardedState

Own rebuild-triggering state that ignores writes after the component unmounts.

What it does

useGuardedState(initialData) returns a GuardedValueNotifier. Assigning a different .value rebuilds the owning component, exactly like useState. Once the component unmounts, the notifier is disposed and every later assignment is silently dropped instead of failing Jaspr's disposed-notifier assertion.

Use it for state that is written after an await, a timer, or a browser callback. It removes the IsMounted check that every such write otherwise needs.

Signature and parameters

GuardedValueNotifier<T> useGuardedState<T>(T initialData)

initialData is used only when the hook state is first created. The returned notifier exposes isDisposed for callers that want to skip follow-up work after the owner is gone.

Usage

class SaveButton extends HookComponent {
  const SaveButton({super.key});

  @override
  Component build(BuildContext context) {
    final status = useGuardedState('idle');

    Future<void> save() async {
      status.value = 'saving';
      await repository.save();
      status.value = 'saved';
    }

    return button(onClick: save, [text(status.value)]);
  }
}

Live demo

Interactive useGuardedState demo

Status: idle • late writes are dropped once unmounted

Ownership and lifecycle

The hook owns the notifier and disposes it when the hook is removed. Assignments made while mounted rebuild the owner, including assignments made during a build, which are rendered after the frame. Assignments after disposal change nothing and notify nobody.

Server rendering

The initializer runs on both platforms and must be deterministic. The notifier can be read during server rendering; nothing subscribes there.

Common mistakes

Do not rely on a dropped write to cancel work. Cancel timers, subscriptions, and requests in an effect cleanup, and use the guard only for the final state assignment. Prefer useState when a late write would indicate a bug you want surfaced.

useState keeps strict disposal semantics. useIsMounted remains useful for skipping non-state follow-up work such as navigation or focus after an asynchronous boundary.