Startup & effects

This lab covers effects that wait for the UI, and the ones emitted before there is any UI to receive them.

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1. Buffering. The controller emits a welcome effect in onInit, before the page can listen. With Buffer effects on, the effect waits and a welcome message appears. Turn it off: the controller is recreated and the effect is lost.
2. Validation. Enter a name shorter than 3 characters and press Save name to see the failure reported through state. Enter a valid one to save it.
3. A dialog with a result. Press Ask confirmation. The intent awaits the user’s answer through emitAndWaitSideEffect; choose Yes or No and watch the status. If you wait, the call times out and reports No answer in time.
4. A missing handler. Press Trigger unhandled effect. No handler is registered for it, so the awaited result fails with a StateError instead of hanging, and the status line shows the failure.

The key line

class SplashController extends JController<SplashState> {
  SplashController() : super(const SplashState(), effectBufferSize: 8);

  @override
  void onInit() => emitSideEffect(ShowWelcome());
}

Details, including what happens when the buffer is full or the controller is disposed, are in the effects guide. The lab source shows the handler and the dialog helper.