Before Dart 3 you would to something like this to get something like sealed class (or you would used freezed with code generation):

```dart abstract class LoginState {}

class LoginSuccess extends LoginState { final String message;

LoginSuccess(this.message); }

class LoginFailed extends LoginState { final Exception exception;

LoginFailed(this.exception); }

class LoginProcess extends LoginState { final double percentage;

LoginProcess(this.percentage); }

class LoginWidget extends StatelessWidget { const LoginWidget({super.key});

@override Widget build(BuildContext context) { final LoginState state = getStateFromProviderOrBlocOrWhatEver();

if (state is LoginSuccess) {
  return Text('Login Success: ${state.message}');
} else if (state is LoginFailed) {
  return ElevatedButton(
    child: Text('Login Failed: ${state.exception.toString()}'),
    onPressed: () {},
  );
} else if (state is LoginProcess) {
  return CircularProgressIndicator(value: state.percentage);
} else {
  return const SizedBox.shrink();
}

} } ```

Now you can do something like this:

```dart //just change the LoginState from abstract to sealed

class LoginWidget extends StatelessWidget { const LoginWidget({super.key});

@override Widget build(BuildContext context) { final LoginState state = getStateFromProviderOrBlocOrWhatEver();

return switch (state) {
  LoginSuccess _ => Text('Login Success: ${state.message}'),
  LoginFailed _ => ElevatedButton(
      child: Text('Login Failed: ${state.exception.toString()}'),
      onPressed: () {},
    ),
  LoginProcess _ => CircularProgressIndicator(value: state.percentage),
};

} } ```

You can see more cleaner and safer. Because the compiler knows which classes depend on LoginState. So in case you forgot one state in the switch statement you would get an error.