q1_answer.dart

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

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

class CountController extends StateNotifier<AsyncValue<int>> {
  CountController() : super(const AsyncData<int>(0));

  Future<void> up() async {

    //because of it's loading
    // state = const AsyncLoading<int>();

    state = await AsyncValue.guard<int>(() async {
      print(state.value);

      ///value is null??
      final current = state.value ?? 0;
      return current + 1;
    });

    // state = AsyncValue.data((state.value ?? 0 )+ 1);
  }
}

final countProvider =
    StateNotifierProvider.autoDispose<CountController, AsyncValue<int>>((ref) {
  return CountController();
});

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: darkBlue,
      ),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends ConsumerWidget {
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    var count = ref.watch(countProvider);
    return Column(
      children: [
        Text(
          'Count: ${count.value}',
          style: Theme.of(context).textTheme.headline4,
        ),
        ElevatedButton(
          onPressed: () => ref.read(countProvider.notifier).up(),
          style: ElevatedButton.styleFrom(
            shape: const StadiumBorder(),
          ),
          child: const Text('up'),
        )
      ],
    );
  }
}