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Reactive Flutter
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| import 'package:flutter/material.dart'; | |
| import 'dart:collection'; | |
| import 'dart:async'; | |
| final Color darkBlue = Color.fromARGB(255, 18, 32, 47); | |
| void main() { | |
| runApp(MyApp()); | |
| } | |
| class MyApp extends StatelessWidget { | |
| @override | |
| Widget build(BuildContext context) { | |
| return MaterialApp( | |
| theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue), | |
| debugShowCheckedModeBanner: false, | |
| home: Scaffold( | |
| body: Center( | |
| child: DemoWidget(), | |
| ), | |
| ), | |
| ); | |
| } | |
| } | |
| class DemoWidget extends StatelessWidget { | |
| final Signal signal; | |
| DemoWidget() : signal = Signal<int>(0) { | |
| Timer.periodic(Duration(seconds: 1), (timer) { | |
| signal.write(signal.read() +1); | |
| }); | |
| } | |
| @override | |
| Widget build(BuildContext context) { | |
| return Reactive(() => Text('Count: ${signal.read()}', style: Theme.of(context).textTheme.headline4)); | |
| } | |
| } | |
| final context = List<Subscription>.empty(growable: true); | |
| void subscribe( | |
| Subscription running, LinkedHashSet<Subscription> subscriptions) { | |
| subscriptions.add(running); | |
| running.dependencies.add(subscriptions); | |
| } | |
| void cleanup(Subscription running) { | |
| for (final dep in running.dependencies) { | |
| dep.remove(running); | |
| } | |
| running.dependencies.clear(); | |
| } | |
| class Signal<T> { | |
| final LinkedHashSet<Subscription> subscriptions = | |
| LinkedHashSet<Subscription>(); | |
| T value; | |
| Signal(this.value); | |
| T read() { | |
| if (context.isNotEmpty) { | |
| final running = context[context.length - 1]; | |
| subscribe(running, subscriptions); | |
| } | |
| return value; | |
| } | |
| void write(nextValue) { | |
| value = nextValue; | |
| for (final sub in subscriptions.toList()) { | |
| sub.execute(); | |
| } | |
| } | |
| } | |
| class Subscription { | |
| Subscription(this.execute, this.dependencies); | |
| Function execute; | |
| LinkedHashSet<LinkedHashSet<Subscription>> dependencies; | |
| } | |
| class Effect { | |
| final Function fn; | |
| late Subscription running; | |
| Effect(this.fn) { | |
| running = | |
| Subscription(_execute, LinkedHashSet<LinkedHashSet<Subscription>>()); | |
| _execute(); | |
| } | |
| void _execute() { | |
| cleanup(running); | |
| context.add(running); | |
| try { | |
| fn(); | |
| } finally { | |
| context.removeLast(); | |
| } | |
| } | |
| } | |
| class Reactive extends StatefulWidget { | |
| final Widget Function() widgetFunction; | |
| const Reactive(this.widgetFunction, {Key? key}) : super(key: key); | |
| @override | |
| State<Reactive> createState() => _ReactiveState(); | |
| } | |
| class _ReactiveState extends State<Reactive> { | |
| var firstTime = true; | |
| Widget? results; | |
| @override | |
| void initState() { | |
| super.initState(); | |
| Effect(() { | |
| results = widget.widgetFunction(); | |
| if (!firstTime) { | |
| setState(() {}); | |
| } else { | |
| firstTime = false; | |
| } | |
| }); | |
| } | |
| @override | |
| Widget build(BuildContext context) { | |
| return results!; | |
| } | |
| } |
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