How to apply MVC or design pattern in flutter?

Question

I am trying to include biometric authentication using local_auth package. This is used when the app starts. The fingerprint is used to determine whether the user is the owner of the phone. If it is confirmed, they will be taken to the home page. The below code works but what I would like to apply on the below code is MVC or design pattern. Can someone guide me?

class LoginOptionState extends State<LoginOption> {
  final LocalAuthentication auth = LocalAuthentication();
  String _authorized = 'Not Authorized';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: new Container(
            child: Center(
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[
          new Column(
            children: <Widget>[
              Text("Touch ID"),
              SizedBox(height: 10),
              GestureDetector(
                  child: Image.asset(
                    "assets/",
                  ),
                  onTap: _authenticate),
            ],
          ),
        ],
      ),
    )));
  }

  Future<void> _authenticate() async {
    bool authenticated = false;
    try {
      authenticated = await auth.authenticateWithBiometrics(
          localizedReason: 'Scan your fingerprint to authenticate',
          useErrorDialogs: true,
          stickyAuth: false);
    } on PlatformException catch (e) {
      print(e);
    }
    if (!mounted) return;

    setState(() {
      _authorized = authenticated
          ? Navigator.pushNamed(context, homePageViewRoute)
          : 'Not Authorized';
    });
  }
}

Answer 1

Use the excellent library by Greg Perry mvc_pattern. Quick start sample code and explanation is provided on the link.

Here is a quick start example of the classic counter app, from the link above:

The view:

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  // Fields in a Widget subclass are always marked "final".

  static final String title = 'Flutter Demo Home Page';

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

class _MyHomePageState extends State<MyHomePage> {

  final Controller _con = Controller.con;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              widget.title,
            ),
            Text(
              '${_con.counter}',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(
              _con.incrementCounter
          );
        },
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

Controller class:

class Controller extends ControllerMVC {
  /// Singleton Factory
  factory Controller() {
    if (_this == null) _this = Controller._();
    return _this;
  }
  static Controller _this;

  Controller._();

  /// Allow for easy access to 'the Controller' throughout the application.
  static Controller get con => _this;

  int get counter => _counter;
  int _counter = 0;
  void incrementCounter() => _counter++;
}

Now the above code refactored, to add a model:

int get counter => Model.counter;
  void incrementCounter() {
    /// The Controller knows how to 'talk to' the Model. It knows the name, but Model does the work.
    Model._incrementCounter();
  }

And finally the model class:

class Model {
  static int get counter => _counter;
  static int _counter = 0;
  static int _incrementCounter() => ++_counter;
}

However make sure you upgrade flutter to version 1.13.0. At least for me, I was getting several build errors in lower versions.

Answer 2

Karee is a set of tools that implementes MVC design in Flutter. It help you to manage your Controllers, your routes, your screens and more. Refer to karee github wiki to get documentation.

You Can use Karee . It supports Flutter 2.X.X

To installation run npm install -g karee Then karee create After creating a New Flutter project based on Karee you can add new controller

Sample Code

Creating à New controller

    Karee generate --controller --path auth Authentication

Generated file under lib/app/controllers/auth/AuthenticationController

@Controller
class AuthenticationController {

       login(username, password) {

                /// Your custom code

       }
}

Add route

   Route.on('/login', 'AuthenticationController@login');

Use in your Screen

   var authUser = KareeRouter.goto('/login', parameter:[username, password]);