immutable state, correct riverpod example

main.dart

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

// A simple counter class with immutable state
class Counter {
  final int value;
  Counter(this.value);

  // Method to return a new instance with an incremented value
  Counter copyWith({int? value}) {
    return Counter(value ?? this.value);
  }
}

// Creating a StateNotifier for the counter
class CounterNotifier extends StateNotifier<Counter> {
  CounterNotifier() : super(Counter(0));

  void increment() {
    state = state.copyWith(value: state.value + 1); // Creating a new instance with copyWith
  }
}

// Creating a provider for the CounterNotifier
final counterProvider = StateNotifierProvider<CounterNotifier, Counter>((ref) {
  return CounterNotifier();
});

void main() {
  runApp(ProviderScope(child: MyApp()));
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Immutable State Example with StateNotifier')),
        body: Center(child: CounterWidget()),
      ),
    );
  }
}

class CounterWidget extends ConsumerWidget {
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final counter = ref.watch(counterProvider);

    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text('Counter value: ${counter.value}'),
        SizedBox(height: 20),
        ElevatedButton(
          onPressed: () {
            // Calling increment on the notifier
            ref.read(counterProvider.notifier).increment();
          },
          child: Text('Increment'),
        ),
      ],
    );
  }
}