I use a MVVM Approach like it is described here https://www.filledstacks.com/post/flutter-architecture-my-provider-implementation-guide/

with the Stacked package

https://pub.dev/packages/stacked

Service Locator (Dependency Injection)

• The package get_it is used for this
  • https://pub.dev/packages/get_it
• can be found in locator.dart
  • register the Service there like this

Services - Repositories

All data is stored in repositories and also most of the logic will be done here. View Models just call the required functions from services or repositories.

• If a new service is added it needs to be added to get_it in the locator.dart

  setupLocator() {
    getIt.registerSingleton(AuthService());
    getIt.registerSingleton(Api());
    getIt.registerSingleton(SharedPreferencesHelper());
  }
  
  //Calling a service in e.g. a viewModel
  getIt<AuthService>().logout();
  

Views

The folder /views holds Screens and View Models

• /screens

  • The Base Widget in the build method is ViewModelProvider from the link above. This is basically just a Consumer which listens to changes notifed in the View Models
  • In 90% of the cases there is no statemanagement done within a screen.
    • Exceptions are some times dialogs or if it is really just one variable and easy to understand

  // View
  class HomeView extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      // Using the reactive constructor gives you the traditional viewmodel
      // binding which will excute the builder again when notifyListeners is called.
      return ViewModelBuilder<HomeViewModel>.reactive(
        viewModelBuilder: () => HomeViewModel(),
        onModelReady: (model) => model.initialise(),
        builder: (context, model, child) => Scaffold(
          floatingActionButton: FloatingActionButton(
            onPressed: () {
              model.updateTitle();
            },
          ),
          body: Center(
            child: Text(model.title),
          ),
        ),
      );
    }
  }
  

• /viewmodels

  • The View Models extend a BaseViewmodel which extends Change Notifier and the state is held here and updated with notifyListeners()

  abstract class BaseViewModel extends ChangeNotifier {
    bool isLoading = false;
  
    void setLoading(bool loading) {
      isLoading = loading;
      notifyListeners();
    }
  }
  
  class HomeViewModel extends BaseViewModel {}
  

• /widgets

  • Widgets that can reused for multiple screens or widgets that are a lot of code

Routing

Routing is done with the help of Get → https://pub.dev/packages/get

• can be found in router.dart
• Is also used for showing dialogs from a view model
• With this package you can use navigation without context
• Adding a new route