Flutter AppRun

A lightweight, easy-to-use, event-driven state management system, highly inspired by AppRun JS.

Features

Use events to drive state changes, easy to understand.
Use pure functions to update the state, easy to test state changes.
The events also drive UI updates, no need to use setState.
The local events are scoped to the widget, no need to worry about the global events.
The global events are used to communicate between widgets, no need to use Provider or Bloc.
Fully support asynchronous state changes.

Getting started

Install it using pub:

flutter pub add flutter_apprun

And import the package:

import 'package:flutter_apprun/flutter_apprun.dart';

Usage

Use AppRunWidget in your widget tree.

AppRunWidget(
  state: initialState,
  update: update,
  builder: (BuildContext context, state) {
    return ... // widget tree biuld from the state
  }
)

The state is the initial state
The update is the collection of event handlers.
The builder is to display the state, which is called whenever the state changes.
Use app.run to trigger global events.
Use AppRun.of(context).run to trigger local events.

Example

A counter page with two buttons to increment and decrement the counter.

// Define the initial state
int initialState = 0;

// Define the event handler collection in a map
int add(int state, int delta) => state + delta;
Map update = {
  '@add': add,                      // global event
  '+1': (state) => add(state, 1),   // local event
  '-1': (state) => add(state, -1),  // local event
};

// Use the AppRunWidget in your widget tree
class HomePage extends StatelessWidget {
  final String title;

  const HomePage({super.key, required this.title});

  @override
  Widget build(BuildContext context) {
    return AppRunWidget(
      state: initialState,
      update: update,
      builder: (BuildContext context, state) {
        return Scaffold(
          appBar: AppBar(
            title: Text(title),
          ),
          body: Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text(
                  '$state',
                  style: Theme.of(context).textTheme.headlineMedium,
                ),
              ],
            ),
          ),
          floatingActionButton: Column(
            mainAxisAlignment: MainAxisAlignment.end,
            children: [
              FloatingActionButton(
                heroTag: 'minus',
                // onPressed: () => app.run('@add', -1),  // global event
                onPressed: () => AppRun.of(context).run('-1'), // local event
                tooltip: 'Decrement',
                child: const Icon(Icons.remove),
              ),
              FloatingActionButton(
                heroTag: 'plus',
                // onPressed: () => app.run('@add', 1), // global event
                onPressed: () => AppRun.of(context).run('+1'), // local event
                tooltip: 'Increment',
                child: const Icon(Icons.add),
              ),
            ],
          ),
        );
      },
    );
  }
}

License

MIT License