import 'package:riverpod/riverpod.dart';

void main() {
  final container = ProviderContainer();
  
  container.listen<Counter>(counter, (prev, value) {
    print('count: ${value.count}');
  }, fireImmediately: true);
  
  container.read(counter).increment();
}

class Counter {
  Counter({required this.count, required this.increment});
  final int count;
  
  final void Function() increment;
  
  Counter copyWith({int? count}) {
    return Counter(count: count ?? this.count, increment: increment);
  }
}


final counter = Provider<Counter>((ref) {
  return Counter(
    count: 0,
    increment: () {
      ref.state = ref.state.copyWith(count: ref.state.count + 1);
    },
  );
});