A simple, dart native state management library for Flutter (Actually, it's just MVVM)

A dart native framework agnostic state management library that won't touch the build method of your UI. It's an alternative approach to BloC or Provider that allows you to separate state logic from your UI without any framework specific code, your build method will be pure Flutter code again and not bloated with 3rd party code. You can use it for any architecture you like and don't need to introduce further libraries if you would like to share state between your UIs, as it is in BloC. It's all in your own hands.

You don't have to learn any magic, state management is completely in your hands again and your build Method won't need any Providers or anything else.

If you like to use BloC or Provider then it's okay.

Just Framework agnostic State Management that won't touch the build method of your UI. You can use it for any architecture you like and don't need

Getting started

Think about how your UI should behave, what states do you need? Create a ViewModel for your Stateful Widget and call your data or domain layer from there. And then you emit a new Event and your UI will handle that state. Your build() of your Flutter Widget is 100% free from any library regarding State management, as it should be. You can focus fully on writing your UI using the Flutter SDK or other UI libs.

Install

Add to your pubspec.yaml dependencies following line

  estado: ^0.0.9

Usage

Here's a simple code snippet how to use this library to separate the state from your UI

// The ViewModel manipulates the state of your UI, it calls your underlying layer, which could be a Repository or a Service / UseCase (in case you use clean architecture)
// possibly orchestrates / aggregates data, and then emits a new event to the UI which causes a state change.
class LoginViewModel extends EventViewModel {
  
  void logIn(String email, String password) {
    // LoadingState could be a State defined in a common package or so
    notify(LoadingEvent(isLoading: true));
    
    authRepository.login(email, password);
    
    // let's assume login was successful
    notify(LoadingEvent(isLoading: false));
    notify(OnLoginSuccessfulEvent());
  }
}

// A simple LoginSuccessfulEvent that indicates the UI that the login was successful
class LoginSuccessfulEvent extends ViewEvent{
  LoginSuccessfulState() : super();
}

// A simple wrapper around the State object, which hold now a ViewModel and takes care of the lifecycle handling
// and gives you a callback when your ViewModel is ready to use and when it emits a new event.
class LoginUiState extends ViewState<LoginViewModel, LoginWidget> {
  bool _loginSuccessful = false;
  bool _isLoading = false;
  
  
  @override
  Widget build(BuildContext context) {
    // build your pure Flutter UI here, no Providers or anything else needed.
    return Container(
      child: _isLoading ? CircularProgressIndicator() : 
      Column(children:[]),
    );
  }
  
  @override
  void notify(ViewModelEvent event) {
    setState(() {
      switch(event.runtimeType) {
          case LoginSuccessfulEvent:
            // do something with the event, maybe navigate to another screen
            break;
        case LoadingEvent:
            _isLoading = (event as LoadingEvent).isLoading;
            break;
      }
    });
  }
  
  @override
  LoginViewModel buildViewModel() {
    // do your ViewModel initialization and dependency injection here
    return LoginViewModel();
  }
  
  @override
void onViewModelReady() {
    // called after view was initialized and ready to be updated
    // this.viewModel.logIn("email", "password");
  }
  
}

Additional information

If you wish to contribute feel free to create a PR at the github repo. For bugs or feature requests you can create an Issue.