flutter_micro_app 0.4.0

A package to speed up the creation of micro apps structure in Flutter applications

A package to speed up the creation of micro apps structure in Flutter applications (beta version)

Monolithic distribution with multiplatform independent components development, inspired in frameworks such as Single SPA and Systemjs.

[coming soon] This diagram shows up the initial proposal about layers, their relationships and dependencies.

⛵️ Navigation between pages

Use [NavigatorInstance] to navigate between pages

NavigatorInstance.pop();
NavigatorInstance.pushNamed();
NavigatorInstance.pushNamedNative();
NavigatorInstance.pushReplacementNamed();
NavigatorInstance ...

📲 Open native (Android/iOS) pages, in this way

It needs native implementation, you can see an example inside Android directory | coming soon, examples and modules to iOS, Desktop and Web, too.

// If not implemented, always return null
final isValidEmail = await NavigatorInstance.pushNamedNative<bool>(
    'emailValidator',
    arguments: 'validateEmail:[e-mail]'
);
print('Email is valid: $isValidEmail');

// Listen to all flutter navigation events
NavigatorInstance.eventController.flutterLoggerStream.listen((event) {
    logger.d('[flutter: navigation_log] -> $event');
});

// Listen to all native (Android/iOS) navigation events (if implemented)
NavigatorInstance.eventController.nativeLoggerStream.listen((event) {});

// Listen to all native (Android/iOS) navigation requests (if implemented)
NavigatorInstance.eventController.nativeCommandStream.listen((event) {});

---

⚙️ Define micro app configurations and contracts

Configure the preferences (optional)

  MicroAppPreferences.update(
    MicroAppConfig(
      nativeEventsEnabled: true, // If you want to dispatch and listen to events between native(Android/iOS) [default = false]
      pathSeparator: MicroAppPathSeparator.slash // It joins the routes segments using slash "/" automatically
    )
  );

🗺 Register all routes

This is just a suggestion of routing strategy (Optional) It's important that all routes are availble out of the projects, avoiding dependencies between micro apps. Create all routes inside a new package, and import it in any project as a dependency. This will make possible to open routes from anywhere in a easy and transparent way.

Create the routing package: flutter create --template=package micro_routes

// Export all routes
import 'package:flutter_micro_app/flutter_micro_app.dart';

class Application1Routes implements MicroAppRoutes {
  @override
  MicroAppBaseRoute get baseRoute => MicroAppBaseRoute('application1');
  String get page1 => baseRoute.path('page1');
  String get page2 => baseRoute.path('page2', ['segment1', 'segment2']);
}

For example, you can open a page that is inside other MicroApp, in this way:

NavigatorInstance.pushNamed(OtherMicroAppRoutes().specificPage);
NavigatorInstance.pushNamed(Application1Routes().page1);

🤝 Expose all pages throuth a contract MicroApp (Inside external projects or features folder)

import 'package:micro_routes/exports.dart';

class Application1MicroApp extends MicroApp with Application1Routes {

  @override
  List<MicroAppPage> get pages => [
        MicroAppPage(name: baseRoute.name, builder: (context, arguments) => const Initial()),
        MicroAppPage(name: page1, builder: (context, arguments) => const Page1()),
        MicroAppPage(name: page2, builder: (context, arguments) {
            final page2Params.fromMap(arguments);
            return Page2(params: page2Params);
        }),
      ];
}

🚀 Initialize the host, registering all micro apps

• MicroHost is also a MicroApp, so you can register pages here too.
• MyApp needs to extends MicroHostStatelessWidget or MicroHostStatefulWidget
• The MicroHost is the root widget, and it has all MicroApps, and the MicroApps has all Micro Pages and associated MicroRoutes.

void main() {
    runApp(MyApp());
}

class MyApp extends MicroHostStatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      navigatorKey: NavigatorInstance.navigatorKey, // Required
      onGenerateRoute: onGenerateRoute, // [onGenerateRoute] this is created automatically, so just use it, or override it, if needed.
      initialRoute: baseRoute.name,
      navigatorObservers: [
        NavigatorInstance // Add NavigatorInstance here, if you want to get didPop, didReplace and didPush events
      ],
    );
  }

  // Base route of host application
  @override
  MicroAppBaseRoute get baseRoute => MicroAppBaseRoute('/');

  // Register all root [MicroAppPage]s here
  @override
  List<MicroAppPage> get pages => [
        MicroAppPage(name: baseRoute.name, builder: (_, __) => const HostHomePage())
      ];

  // Register all [MicroApp]s here
  @override
  List<MicroApp> get microApps => [MicroApplication1(), MicroApplication2()];
}

---

🤲 Handling micro apps events

👀 As soon as I can, I'll do possible to filtering by event name, too.

🗣 Dispatches events to all handlers that listen to channels 'user_auth' and 'chatbot'

MicroAppEventController()
    .emit(const MicroAppEvent<Map<String, dynamic>>(
        name: 'my_event',
        payload: {'data': 'lorem ipsum'},
        channels: ['user_auth', 'chatbot'])
    );

🗣 Dispatches events directly to handler with id = '0001' (only)

MicroAppEventController()
    .emit(const MicroAppEvent(
        name: 'my_event',
        payload: {},
        id: '0001')
    );

🗣 Dispatches events to handlers that listen to String event type

MicroAppEventController()
    .emit<String>(const MicroAppEvent(
        name: 'my_event',
        payload: 'some string here')
    );

🗣 Dispatches events to handlers that listen to String event type, and channels 'user_auth' and 'wellcome'

MicroAppEventController()
    .emit<String>(const MicroAppEvent<String>(
        name: 'my_event',
        payload: 'some string here'),
        channels: ['user_auth', 'wellcome']
    );

🌐 It is possible to wait for other micro apps to respond to the event you issued, but make sure someone else will respond to your event, otherwise you will wait forever 😢

.getFirstResult() will return the first response(fastest) among all micro apps that eventually can respond to this same event.

For example, if you request a JWT token to all micro apps(broadcast), the first response(if more than one MA can respond) will end up your request with the resultSucces value or with a resultError, from the fastest micro app.

  final result = await MicroAppEventController()
    .emit(MicroAppEvent<Map<String, String>>(
      name: 'get_jwt',
      payload: const {'userId': 'ABC123'},
      channels: const ['jwt'],
    )
  ).getFirstResult(); // This will return the first response(fastest) among all micro app that eventually can respond to this same the event

  print(result);

Later, when some micro app that is listening to same channel get triggered, it can answer success or error.

// results success
event.resultSuccess(['success message by Wally West', 'your token, Sir.']);

// results error
event.resultError(['error message by Barry Allen', 'my bad 🤦']);

// Who will respond faster? native? flutter?
// If you don't want to take that risk, just deal with the List<Future> response.

🦻 Listen to events (MicroApp)s

MicroApp has a getter method that must be overwritten, it's called microAppEventHandler

Some example scenarios:

// It listen to all events
@override
  MicroAppEventHandler? get microAppEventHandler =>
      MicroAppEventHandler((event) => logger.d([ event.name, event.payload]));

// It listen to events with channels "chatbot" and "user_auth"
@override
  MicroAppEventHandler? get microAppEventHandler =>
      MicroAppEventHandler((event) {
        // User auth feature, asked to show a popup :)
        myController.showDialog(event.payload);
      }, channels: ['chatbot', 'user_auth']);

// It listen to events with type String (only)
@override
  MicroAppEventHandler<String>? get microAppEventHandler =>
      MicroAppEventHandler((event) {
        // Use .cast() to automatically cast the payload data to String? type
        logger.d(event.cast()); 
      });

// It will be fired for every event, even if the value is the same (distinct = false)
@override
  MicroAppEventHandler<String>? get microAppEventHandler =>
      MicroAppEventHandler((event) {
        logger.d(event.cast()); 
      }, distinct: false);

Listen to events inside widgets (If need BuildContext)

It can be achieved, registering the event handlers and unregistering them manually, or if you prefer, use a mixin called HandlerRegisterMixin to dispose handlers automatically when widget is disposed

Using mixin HandlerRegisterMixin example:

class MyWidgetState extends State<MyWidget> with HandlerRegisterMixin {

  @override
  void initState() {
    registerEventHandler(MicroAppEventHandler<String>((event) {
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(
        content: Text(event.cast()),
      ));
    }, channels: const ['show_snackbar'], distinct: false));

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

Managing events

MicroAppEventController().unregisterHandler(id: '123');
MicroAppEventController().unregisterHandler(handler: handlerInstance);
MicroAppEventController().unregisterHandler(channels: ['user_auth']);
MicroAppEventController().pauseAllHandlers();
MicroAppEventController().resumeAllHandlers();
MicroAppEventController().unregisterAllHandlers();

🦻 Initiating an event subscription anywhere in the application (inside a StatefulWidget, for example)

Using subscription

final subscription = MicroAppEventController().stream.listen((MicroAppEvent event) {
    logger.d(event);
  });

// later, in dispose method of the widget
@override
void dispose() {
    subscription.cancel();
    super.dispose();
}

Using handler

MicroAppEventController().registerHandler(MicroAppEventHandler(id: '1234'));

// later, in dispose method of the widget
@override
void dispose() {
    MicroAppEventController().unregisterHandler(id: '1234');
    super.dispose();
}

🏭 Using the pre-built widget MicroAppWidgetBuilder to display data on the screen

It can be used to show visual info on the screen. In this example, it shows a button and the label changes when user clicks on the button

ℹ️ When user dispatched an event in the same channel that the widget is listening to, the widget redraw the updated info on the screen.

MicroAppWidgetBuilder(
  initialData: MicroAppEvent(name: 'my_event', payload: 0),
  channels: const ['widget_channel'],
  builder: (context, eventSnapshot) {
    if (eventSnapshot.hasError) return const Text('Error');
    return ElevatedButton(
      child: Text('Widget count = ${eventSnapshot.data?.payload}'
      ),
      onPressed: () {
        MicroAppEventController().emit(MicroAppEvent<int>(
            name: 'my_event',
            payload: ++count,
            channels: const ['widget_channel']));
      },
    );
  }
)

---

📝 Overriding onGenerateRoute method

If it fails to get a page route, ask for native(Android/iOS/Desktop/Web) to open the page

  @override
  Route? onGenerateRoute(RouteSettings settings, {bool? routeNativeOnError}) {
    //! If you wish native app receive requests to open routes, IN CASE there
    //! is no route registered in Flutter, please set [routeNativeOnError: true]
    return super.onGenerateRoute(settings, routeNativeOnError: true);
  }

If it fails to get a page route, show a default error page

  @override
  Route? onGenerateRoute(RouteSettings settings, {bool? routeNativeOnError}) {
    
    final pageRoute = super.onGenerateRoute(settings, routeNativeOnError: false);

    if (pageRoute == null) {
       // If pageRoute is null, this route wasn't registered(unavailable)
       return MaterialPageRoute(
           builder: (_) => Scaffold(
                 appBar: AppBar(),
                 body: const Center(
                   child: Text('Page Not Found'),
                 ),
            ));
    }
    return pageRoute;
  }
     

📎 The following table shows how Dart values are received on the platform side and vice versa

Dart	Kotlin	Swift	Java
null	null	nil	null
bool	Boolean	NSNumber(value: Bool)	java.lang.Boolean
int	Int	NSNumber(value: Int32)	java.lang.Integer
int, if 32 bits not enough	Long	NSNumber(value: Int)	java.lang.Long
double	Double	NSNumber(value: Double)	java.lang.Double
String	String	String	java.lang.String
Uint8List	ByteArray	FlutterStandardTypedData(bytes: Data)	byte[]
Int32List	IntArray	FlutterStandardTypedData(int32: Data)	int[]
Int64List	LongArray	FlutterStandardTypedData(int64: Data)	long[]
Float32List	FloatArray	FlutterStandardTypedData(float32: Data)	float[]
Float64List	DoubleArray	FlutterStandardTypedData(float64: Data)	double[]
List	List	Array	java.util.ArrayList
Map	HashMap	Dictionary	java.util.HashMap

👨‍💻👨‍💻 Contributing

Contributions of any kind are welcome!