MVI - Model-View-Intent for Flutter

A clean and efficient implementation of the MVI (Model-View-Intent) pattern for Flutter using ValueListenable for reactive state management.

This package provides a robust architecture to implement the MVI pattern in your Flutter projects, helping you build reactive, predictable, and testable user interfaces.

What is MVI?

MVI is a unidirectional data flow architecture pattern that helps manage application state predictably. It consists of three main components:

• Model: Represents the state of the application. It's an immutable object that holds all the data needed for the view.
• View: The user interface (UI) that displays the state. In Flutter, this would be your widgets.
• Intent: Represents an intention to change the state. These are usually triggered by user interactions with the UI.

Additionally, this implementation supports Effects for handling one-time side effects like navigation, showing snackbars, or other UI actions that don't affect state.

Core Components

Base Classes

• BaseState: Abstract base class for all state objects. States should be immutable.
• BaseEvent: Abstract base class for all events (intents) that can trigger state changes.
• BaseEffect: Abstract base class for all effects (one-time side effects).

ViewModels

• SimpleViewModel: For state management without effects.
• ViewModel: For state management with effects support.

Mixins

• SimpleViewModelMixin: Mixin for connecting widgets to SimpleViewModels.
• ViewModelMixin: Mixin for connecting widgets to ViewModels with effects support.

State Management with ValueListenable

This MVI implementation uses Flutter's built-in ValueListenable and ValueNotifier for reactive state management. The state is observable and automatically triggers UI rebuilds when changed.

Getting Started

Add the package to your pubspec.yaml:

dependencies:
  mvi: ^2.0.0

Then, run flutter pub get.

Example

Check the examples folder for complete implementations and tests:

• examples/counter/ - Simple counter app demonstrating basic MVI pattern
• examples/login_posts_list/ - Complete app with login flow and data fetching

Features

• ✅ Reactive State Management: Built on Flutter's ValueListenable
• ✅ Effects Support: Handle side effects like navigation and dialogs
• ✅ Performance Optimized: Selectors prevent unnecessary rebuilds
• ✅ Debug Support: Built-in logging for development
• ✅ Testable: Easy to unit test ViewModels and business logic

Contributing

Contributions are welcome! Please feel free to submit a pull request or open an issue.