Command Pattern in Dart

base.command.dart

abstract class BaseCommand<T> {
  BuildContext _context;

  BaseCommand(BuildContext context) {
    /// Get root context
    /// If we're passed a context that is known to be root, skip the lookup, it will throw an error otherwise.
    _context = (context == _lastKnownRoot) ? context : context.read();
    _lastKnownRoot = _context;
  }

  T locate<T>() => _context.read();

  static BuildContext _lastKnownRoot;

  Future<T> run();
}

login.command.dart

class LoginCommand extends BaseCommand<bool> {
  final String user;
  final String pass;
  
  LoginCommand(BuildContext context, {this.user, this.pass}) : super(context);

  @override
  run() async {
    UserService userService = locate();
    UserCubit userBloc = locate();
    
    // Await some service call
    bool loginSuccess = await userService.login(user, pass);
    
    // Update appModel with current user. Any views bound to this will rebuild
    userBloc.update(loginSuccess ? user : null);

    // Return the result to whoever called us, in case they care
    return loginSuccess;
  }
  
}

user.cubit.dart

class UserCubit extends Cubit<User> {
  UserCubit() : super(null);

  void update(String user) => emit(User(user));
}

class User {
  final String user;

  User(this.user);
}

user.service.dart

class UserService {
  Future<bool> login(String user, String pass) => Future.value(true);
}