get_it 3.1.0

Simple direct Service Locator that allows to decouple the interface from a concrete implementation and to access the concrete implementation from everywhere in your App"

example/lib/main.dart

import 'package:flutter/material.dart';
import 'package:get_it/get_it.dart';
import 'package:get_it_example/app_model.dart';

// This is our global ServiceLocator
GetIt getIt = GetIt.instance;

void main() {
  
  getIt.registerSingleton<AppModel>(AppModelImplementation(),
      signalsReady: true);

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  initState() {
    // Access the instance of the registered AppModel
    getIt<AppModel>().addListener(update);
    // Alternative
    // getIt.get<AppModel>().addListener(update);

    super.initState();
  }

  @override
  void dispose() {
    getIt<AppModel>().removeListener(update);
    super.dispose();
  }

  update() => setState(() => {});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: StreamBuilder(
            stream: getIt.ready,
            builder: (context, snapshot) {
              if (snapshot.hasData) {
                return Column(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    Text(
                      'You have pushed the button this many times:',
                    ),
                    Text(
                      '${getIt<AppModel>().counter}',
                      style: Theme.of(context).textTheme.display1,
                    ),
                  ],
                );
              } else {
                return Column(
                  mainAxisAlignment: MainAxisAlignment.center,
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Text('Waiting for initialisation'),
                    SizedBox(
                      height: 16,
                    ),
                    CircularProgressIndicator(),
                  ],
                );
              }
            }),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: getIt<AppModel>().incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}