How to use MVVM in flutter?

MVVM (Model-View-ViewModel) is an architectural pattern that separates the application into three layers: the Model, the View, and the ViewModel. Here's how you can use MVVM in Flutter:

1. Model Layer: The model layer is responsible for handling data and business logic. In Flutter, you can create a separate class for your model or use an existing model library like Provider or BLoC.

2. View Layer: The view layer is responsible for displaying the user interface. In Flutter, you can create your user interface using widgets. You can also use third-party libraries like Flutter Material or Cupertino widgets to build your UI.

3. ViewModel Layer: The ViewModel layer acts as a mediator between the View and the Model. It receives user input from the View, processes it with the Model, and then updates the View. In Flutter, you can create a separate class for your ViewModel or use an existing library like Provider or BLoC.

Here are the steps to implement MVVM in Flutter:

1. Create a Model class that holds the data and business logic

class UserModel {
  String name;
  String email;
  String password;

  UserModel({required this.name, required this.email, required this.password});

  bool login() {
    // code to handle user login
    return true;
  }
}

1. Create a View class that displays the user interface.

class LoginView extends StatelessWidget {
  final LoginViewModel viewModel;

  LoginView({required this.viewModel});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextField(
              decoration: InputDecoration(
                hintText: 'Email',
              ),
              onChanged: (value) {
                viewModel.email = value;
              },
            ),
            TextField(
              decoration: InputDecoration(
                hintText: 'Password',
              ),
              onChanged: (value) {
                viewModel.password = value;
              },
            ),
            ElevatedButton(
              onPressed: () {
                viewModel.login();
              },
              child: Text('Login'),
            ),
          ],
        ),
      ),
    );
  }
}

 

1. Create a ViewModel class that handles user input and updates the View.

class LoginViewModel {
  UserModel model;
  String email = '';
  String password = '';

  LoginViewModel({required this.model});

  void login() {
    model.email = email;
    model.password = password;
    if (model.login()) {
      // Navigate to the home page
    } else {
      // Show an error message
    }
  }
}

1. Finally, create an instance of the Model and ViewModel classes and pass them to the View.

void main() {
  UserModel userModel = UserModel(name: 'User', email: '', password: '');
  LoginViewModel loginViewModel = LoginViewModel(model: userModel);
  runApp(MyApp(view: LoginView(viewModel: loginViewModel)));
}

By following these steps, you can implement MVVM architecture in Flutter to build scalable and maintainable applications.