iridescent-tundra-1306

readme.md

iridescent-tundra-1306

Created with <3 with dartpad.dev.

main.dart

import 'dart:math';

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

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

final sourceProvider = FutureProvider((ref) async {
  await Future.delayed(Duration(seconds: 1));

  return Random().nextInt(42);
});

final dependendProvider = FutureProvider((ref) {
  return ref.watch(sourceProvider.selectAsync((data) => data));
});

final doubleProvider = Provider((ref) {
  return ref.watch(dependendProvider).whenData((data) => data * 2);
});

final doubleWithManualCheckingProvider = Provider((ref) {
  final sourceVal = ref.watch(dependendProvider);

  return switch (sourceVal) {
    AsyncValue(hasValue: true, :final value?) => AsyncData(value * 2),
    AsyncError(:final error, :final stackTrace) =>
      AsyncError(error, stackTrace),
    AsyncLoading() || _ => const AsyncLoading(),
  };
});

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ProviderScope(
      child: 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) {
    final sourceVal = ref.watch(sourceProvider);
    final dependendProviderValue = ref.watch(dependendProvider);
    final doubleProviderValue = ref.watch(doubleProvider);
    final doubleWithManualCheckingValue =
        ref.watch(doubleWithManualCheckingProvider);

    print("source: " + sourceVal.toString());
    print("dep: " + dependendProviderValue.toString());
    print("double: " + doubleProviderValue.toString());
    print("double manual: " + doubleWithManualCheckingValue.toString());

    print("---");

    return Column(
      children: [
        Text(sourceVal.toString()),
        Text(dependendProviderValue.toString()),
        Text(doubleProviderValue.toString()),
        Text(doubleWithManualCheckingValue.toString()),
        TextButton(
            onPressed: () {
              print("invalidate");
              ref.invalidate(sourceProvider);
            },
            child: Text("invalidate")),
      ],
    );
  }
}