Flutter未知功能插件df_pod的使用

由于介绍为undefined，以下基于插件名称进行合理推测。df_pod是一个用于Flutter应用状态管理的插件，它提供了类似于ValueNotifier的对象——Pods（"Points of Data"的缩写）。下面将详细介绍如何使用这个插件。

安装与设置

首先，在你的pubspec.yaml文件中添加df_pod作为依赖项：

dependencies:
  df_pod: ^latest_version

然后运行flutter pub get以安装该包。为了确保最佳实践，请更新你的analysis_options.yaml文件如下：

include: package:flutter_lints/flutter.yaml

linter:
  rules:
    prefer_function_declarations_over_variables: false

analyzer:
  errors:
    invalid_use_of_protected_member: error
    invalid_override_of_non_virtual_member: error

快速入门

定义一个Pod

你可以像定义ValueNotifier一样定义一个Pod：

final pNumbers = Pod<List<int>>([1, 2, 3, 4, 5]);

在UI中使用PodBuilder

使用PodBuilder在你的UI中显示数据，类似于ValueListenableBuilder：

PodBuilder(
  pod: pNumbers,
  builder: (context, snapshot) {
    final numbers = snapshot.value!;
    return Text('Count: ${numbers.length}');
  },
);

你也可以使用传统的ValueListenableBuilder：

ValueListenableBuilder(
  valueListenable: _pCounter1,
  builder: (context, value, child) {
    return Text('Count: $value');
  },
);

设置和更新一个Pod

通过set函数设置Pod值，这会触发所有相关的PodBuilder重建：

pNumbers.set([1, 2, 4]);

通过update函数更新Pod值：

pNumbers.update((e) => e..add(5));

处置Pod

当不再需要Pod时，记得手动处置它们：

pNumbers.dispose();

使用多个Pod

你可以使用PodListBuilder来处理多个Pod：

PodListBuilder(
  podList: [pLength, pSum],
  builder: (context, snapshot) {
    final [length, sum] = snapshot.value!.toList();
    return Text('Length is $length and sum is $sum');
  },
);

示例Demo

以下是一个完整的示例代码，演示了如何在Flutter应用中使用df_pod插件：

import 'package:flutter/material.dart';
import 'package:df_pod/df_pod.dart';
import 'package:get_it/get_it.dart';

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

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  const HomePage({Key? key}) : super(key: key);

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("df_pod Example")),
      body: HomePageInterpretedBuilder(
        builder: (context, interpreter) {
          return Column(
            children: [
              PodBuilder(
                pod: interpreter.pUserId,
                builder: (context, userIdSnapshot) {
                  return Text('UserId: ${userIdSnapshot.value}');
                },
              ),
              PodListBuilder(
                podList: [
                  interpreter.pConnectionCount,
                  interpreter.pNotificationCount,
                ],
                builder: (context, podListSnapshot) {
                  final [connectionCount!, notificationCount!] =
                      podListSnapshot.value.toList();
                  final notificationRatio = notificationCount / connectionCount;
                  return Text('Notification ratio: $notificationRatio');
                },
              ),
              OutlinedButton(
                onPressed: () {
                  interpreter.authService.login();
                },
                child: const Text('Login'),
              ),
              OutlinedButton(
                onPressed: () {
                  interpreter.authService.logout();
                },
                child: const Text('Logout'),
              ),
            ],
          );
        },
      ),
    );
  }
}

class HomePageInterpretedBuilder extends StatelessWidget {
  final Widget Function(BuildContext context, HomePageInterpreter interpreter) builder;

  const HomePageInterpretedBuilder({
    Key? key,
    required this.builder,
  }) : super(key: key);

  [@override](/user/override)
  Widget build(BuildContext context) {
    return builder(
      context,
      HomePageInterpreter(
        GetIt.I<AuthService>(),
        GetIt.I<ConnectionService>(),
        GetIt.I<NotificationService>(),
      ),
    );
  }
}

class HomePageInterpreter {
  final AuthService authService;
  final ConnectionService connectionService;
  final NotificationService notificationService;

  HomePageInterpreter(
    this.authService,
    this.connectionService,
    this.notificationService,
  );

  late final pUserId = authService.pUser.map((e) => e!.id);
  late final pNotificationCount = notificationService.pNotifications.map((e) => e!.length);
  late final pConnectionCount = connectionService.pConnections.map((e) => e!.length);
  late final pNotificationRatio = pNotificationCount.reduce(pConnectionCount, (a, b) => a.value / b.value);
}

class AuthService {
  final pUser = Pod<User?>(null);

  late final pIsLoggedIn = pUser.map((e) => e != null);

  Future<void> login() async {
    await Future.delayed(const Duration(seconds: 1), () {
      pUser.set(User('123'));
      GetIt.I.registerLazySingleton<ConnectionService>(() => ConnectionService(this), dispose: (e) => e.dispose());
    });
  }

  Future<void> logout() async {
    await Future.delayed(const Duration(seconds: 1), () {
      pUser.set(null);
      GetIt.I.unregister<ConnectionService>();
    });
  }

  void dispose() {
    pUser.dispose();
  }
}

class ConnectionService {
  final AuthService authService;
  final pConnections = Pod(<User>[]);

  ConnectionService(this.authService);

  void dispose() {
    pConnections.dispose();
  }
}

class User {
  final String id;
  const User(this.id);
}

class NotificationService {
  StreamSubscription<String>? _streamSubscription;
  final pNotifications = Pod(Queue<String>.from([]));

  NotificationService() {
    _startSteam();
  }

  void _startSteam() {
    _stopStream();
    _streamSubscription = Stream.periodic(const Duration(seconds: 5), (count) {
      return ['priority: I love Pods', 'GetIt is nice', 'I like Streams.'][count % 3];
    }).listen(_pushMessage);
  }

  void _pushMessage(String message) {
    pNotifications.update((messages) {
      messages.add(message);
      if (messages.length > 100) {
        messages.removeFirst();
      }
      return messages;
    });
  }

  void _stopStream() {
    _streamSubscription?.cancel();
    _streamSubscription = null;
  }

  void dispose() {
    _stopStream();
    pNotifications.dispose();
  }
}

void onAppStart() {
  GetIt.I
    ..registerLazySingleton<AuthService>(() => AuthService(), dispose: (e) => e.dispose())
    ..registerLazySingleton<NotificationService>(() => NotificationService(), dispose: (e) => e.dispose());
}