flutter_hooks 0.2.0

A flutter implementation of React hooks. It adds a new kind of widget with enhanced code reuse.

example/lib/main.dart

// ignore_for_file: omit_local_variable_types
import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() => runApp(_MyApp());

class _MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Flutter Demo',
      home: _Counter(),
    );
  }
}

class _Counter extends HookWidget {
  const _Counter({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    StreamController<int> countController =
        _useLocalStorageInt(context, 'counter');
    return Scaffold(
      appBar: AppBar(
        title: const Text('Counter app'),
      ),
      body: Center(
        child: HookBuilder(
          builder: (context) {
            AsyncSnapshot<int> count = useStream(countController.stream);

            return !count.hasData
                // Currently loading value from local storage, or there's an error
                ? const CircularProgressIndicator()
                : GestureDetector(
                    onTap: () => countController.add(count.data + 1),
                    child: Text('You tapped me ${count.data} times.'),
                  );
          },
        ),
      ),
    );
  }
}

StreamController<int> _useLocalStorageInt(
  BuildContext context,
  String key, {
  int defaultValue = 0,
}) {
  final controller = useStreamController<int>(keys: <dynamic>[key]);

  // We define a callback that will be called on first build
  // and whenever the controller/key change
  useEffect(() {
    // We listen to the data and push new values to local storage
    final sub = controller.stream.listen((data) async {
      final prefs = await SharedPreferences.getInstance();
      await prefs.setInt(key, data);
    });
    // Unsubscribe when the widget is disposed
    // or on controller/key change
    return sub.cancel;
  }, <dynamic>[controller, key]);
  // We load the initial value
  useEffect(() {
    SharedPreferences.getInstance().then((prefs) async {
      int valueFromStorage = prefs.getInt(key);
      controller.add(valueFromStorage ?? defaultValue);
    }).catchError(controller.addError);
    // ensure the callback is called only on first build
  }, <dynamic>[controller, key]);

  return controller;
}