Bloc getting value error

[gerryau]

Describe the bug
Error saying string value of a bloc state is empty, but the desired result is achieved on device when running.

Expected behavior
No error.

════════ Exception caught by widgets library ═══════════════════════════════════
The following UnexpectedValueError was thrown building BlocBuilder<TodoTimerBlockFormBloc, TodoTimerBlockFormState>(dirty, state: _BlocBuilderBaseState<TodoTimerBlockFormBloc, TodoTimerBlockFormState>#f5386):
"Encountered a ValueFailure at an unrecoverable point. Terminating. Failure was: ValueFailure.empty(failedValue: )"

The relevant error-causing widget was
BlocBuilder<TodoTimerBlockFormBloc, TodoTimerBlockFormState>
package:app/…/todo_timer_form/new_todo_timer_form_page.dart:69
When the exception was thrown, this was the stack
#0 ValueObject.getOrCrash.
package:app/…/core/value_objects.dart:21
#1 Left.fold
package:dartz/src/either.dart:124
#2 ValueObject.getOrCrash
package:app/…/core/value_objects.dart:21
#3 TimerFormScaffold.build.
package:app/…/todo_timer_form/new_todo_timer_form_page.dart:71
#4 BlocBuilder.build
package:flutter_bloc/src/bloc_builder.dart:90
...
════════════════════════════════════════════════════════════════════════════════

@Injectable
class TodoTimerBlockFormBloc
extends Bloc<TodoTimerBlockFormEvent, TodoTimerBlockFormState> {
final ITodoRepository _todoRepository;

TodoTimerBlockFormBloc(this._todoRepository);

@OverRide
TodoTimerBlockFormState get initialState => TodoTimerBlockFormState.initial();

@OverRide
Stream mapEventToState(
TodoTimerBlockFormEvent event,
) async* {
yield* event.map(
initialized: (e) async* {
yield e.initialTodoOption.fold(
() => state,
(initialTodo) {
return state.copyWith(
todo: initialTodo,
);
},
);
},
...

class NewTimerPage extends HookWidget {
final TodoItem selectedTodo;

const NewTimerPage({
Key key,
@required this.selectedTodo,
}) : super(key: key);

@OverRide
Widget build(BuildContext context) {
return BlocProvider(
create: (context) => getIt()
..add(TodoTimerBlockFormEvent.initialized(optionOf(selectedTodo))),
child: BlocConsumer<TodoTimerBlockFormBloc, TodoTimerBlockFormState>(
listener: (context, state) {
...
builder: (context, state) {
return Stack(
children: [
TimerFormScaffold(),
],
);
}
),
);
}
}

class TimerFormScaffold extends StatelessWidget {
@OverRide
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: BlocBuilder<TodoTimerBlockFormBloc, TodoTimerBlockFormState>(
builder: (context, state){
return Text(state.todo.name.getOrCrash());
},
)
),
);
}
}

[felangel]

Hi @gerryau 👋
Thanks for opening an issue!

Can you please provide a link to a sample app which reproduces the issue? Thanks 🙏

[gerryau]

Hey @felangel thanks for your reply, I've just invited you to see the app, where the problem exists. It's under the todo-timer branch. Thanks

[felangel]

Hi @gerryau I am unable to run due to a missing GoogleService-Info.plist. Would it be possible for you to put together a simple sample app which ideally doesn't have a Firebase dependency and reproduces the issue? It would be much easier for me to help if I can easily reproduce the issue locally, thanks!

[gerryau]

No problem @felangel , see link: https://github.com/gerryau/todo-bloc

[felangel]

Hey @gerryau 👋

I took a look and the issue is there is a frame where the TodoTimerState is TodoTimerState.initial() which means that when you call state.todo.name.getOrCrash() it will crash since the todo is empty. This is because the bloc's initial state is TodoTimerState.initial() and when you add the TodoTimerEvent.initialized event it still takes a frame to propagate so the TimerFormScaffold will be rendered at least once where the state has not been updated.

I opened a pull request with one potential fix. Hope that helps!

Closing for now but feel free to comment with additional questions and I'm happy to continue the conversation 👍