Command_it & Result Patterns - an Integration Doubt

[wolf-coder]

I discovered your package by following the Clean Architecture suggestions in the official Flutter documentation. The command-objects case study specifically recommended flutter_command, which led me to your work.

1. That official doc proposed a Command pattern implementation that works with the Result class pattern:

// in ViewModel
HomeViewModel({
  required BookingRepository repo,
}) : _repo = repo {
  loadCommand = Command0(_function)..execute();

late Command0 loadCommand;

Future<Result> _function() async {
  final result = await _repo.getBookingsList();
  switch (result) {
    case Ok<SomeDataClass>():
      ....
    case Error<SomeDataClass>():
      ....
  }
  return result;
}

// in View
ListenableBuilder(
  listenable: widget.viewModel.load,
  builder: (context, child) {
    if (widget.viewModel.loadCommand.running) {
      return const CircularProgressIndicator();
    }

    if (widget.viewModel.loadCommand.error) {
      ...
    }
    if (widget.viewModel.loadCommand.completed) {
      // here
    }
    return child!;
  },
)

• Command library here internally implements the Result class: https://github.com/flutter/samples/blob/main/compass_app/app/lib/utils/command.dart

2. The way I see result pattern works with command_it is by returning Sucess.value and throwing Failure.value:

HomeViewModel({
  required BookingRepository repo,
}) : _repo = repo {
  commandResult = Command.createAsyncNoParam(
    _function,
    initialValue: ,
  );
}

Future<SomeDataClass> _function() async {
  final Result<SomeDataClass> result = await _repo.getBookingsList();
  switch (result) {
    case Ok<SomeDataClass>():
      ....
      return result.value; <---
    case Error<SomeDataClass>():
      ....
      throw '${result.error}' <---
  }
}

However, I'm quite skeptical about this workaround long-term viability. I'm hoping for some insight for robust design pattern (Command and Result).

Lastly, kudos on your work! I'm slowly adapting flutter-it

[escamoteur]

I recommend reading my article https://blog.burkharts.net/practical-flutter-architecture
I also made a full refacoring of the official comass app https://github.com/escamoteur/compass_fork

You should not use a Result type when working with command_it, it's way better just to use it how it is intended
see https://www.droidcon.com/2023/08/07/coding-the-happy-path-with-commands-and-exceptions/

All exceptions in the function that is wrapped by a command are automatically caught and can be observed on the .errors property of the command.