手撸一个Flutter插件实现跨苹果全家桶云同步持久化Key Value数据

前言

作为一个客户端开发者，后端开发一直是我的弱项。虽然GPT的横空出世，让我对后端的开发有一点眉目。但是现实是，能不触碰就不触碰，因为人的精力是有限，如何在有限的时间里发挥最大的作用一直是我的一个追求。所以回到本次主题，我自己上线的一个产品，目前已经成功上线了iOS以及Mac端，如何在不开发后端的情况下实现同步轻量级数据呢？答案是利用Cloud Kit。Cloud Kit是苹果官方API，用于同步同意iCloud账号下设备的数据，包括Key Value Storage、云dataBase、云document等等。通过翻阅pub类似的库，我发现了有以下几个pub包是可以参考的cloud_kit、icloud_storage，但是他们都不是我想要的，要么是不支持Mac、要么是只能同步存储文件，但是我想要同步的其实只是轻量级持久化数据（也是就是iOS下的UserDefault，基于键值存储）。所以没办法了，肝了一晚上我手撸了一个Flutter插件icloud_kv_storage，完美的支持了跨苹果设备iOS、Mac、iPad等的轻量级Key Value数据同步。
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开发过程全解析

创建Flutter插件项目，指定支持iOS、Mac平台

如何创建插件虽然已经很简单，这里我还是点一下。

flutter create icloud_kv_storage -t plugin
cd ./icloud_kv_storage//指定platformsflutter create ./ -t plugin --platforms ios
flutter create ./ -t plugin --platforms macos

先设计Flutter Channel接口

由于是肝了一晚上的产品，非常赶，第一版先只支持同步String数据，后续再支持别的基础数据，如int、double、bool等。


///获取真正的Key，我内部Key都加了flutter前缀，如果要拿真实的Key可以使用此方法
String getRealKey(String key) {throw UnimplementedError('getRealKey()) has not been implemented.');}///原生的CallBack 用于实时刷新数据（如果多台苹果设备都在线，支持实时同步void setNativeCallBack({required GetNativeCallBackFuture onCallBack}) {}///保存数据接口，这里用范型方便后续拓展，虽然第一版只支持StringFuture<void> write<T>({required String key,required T value}) {throw UnimplementedError('write({required String key,required String value}) has not been implemented.');}///读取一个Key的数据接口，同理也是范型Future<T?> read<T>({required String key}) {throw UnimplementedError('read({required String key}) has not been implemented.');}///删除一个keyFuture<void> delete({required String key}) {throw UnimplementedError('delete({required String key}) has not been implemented.');}

原生Swift接口的实现

iOS和Mac实际都是共用Foundation框架，所以我们只需要编写同一套Swift实现，即可同时满足iOS以及Mac。

1.首先定义Channel实现协议


enum CKCommandType: String {case DELETE_VALUEcase GET_VALUEcase SAVE_VALUEcase EMPTY = ""
}protocol CKCommandHandlerProtocol {var COMMAND_NAME: CKCommandType { get }func evaluateExecution(command: String) -> Boolfunc handle(command: String, arguments: Dictionary<String, Any>, result: @escaping FlutterResult) -> Void
}

2.实现增删改查对应methodName的协议

查询一个key对应的协议实现


class CKGetValueHandler: CKCommandHandlerProtocol {var COMMAND_NAME: CKCommandType = .GET_VALUEfunc evaluateExecution(command: String) -> Bool {return CKCommandType(rawValue: command) == COMMAND_NAME}func handle(command: String, arguments: Dictionary<String, Any>, result: @escaping FlutterResult) {if (!evaluateExecution(command: command)) {return}if let key = arguments["key"] as? String {let store = NSUbiquitousKeyValueStore.defaultresult(store.object(forKey: key))} else {result(FlutterError.init(code: "Error", message: "Cannot pass key and value parameter", details: nil))}}}

删除一个Key的实现


class CKDeleteValueHandler: CKCommandHandlerProtocol {var COMMAND_NAME: CKCommandType = .DELETE_VALUEfunc evaluateExecution(command: String) -> Bool {return CKCommandType(rawValue: command) == COMMAND_NAME}func handle(command: String, arguments: Dictionary<String, Any>, result: @escaping FlutterResult) {if (!evaluateExecution(command: command)) {return}if let key = arguments["key"] as? String {let store = NSUbiquitousKeyValueStore.defaultstore.removeObject(forKey: key)result(true)} else {result(FlutterError.init(code: "Error", message: "Cannot pass key parameter", details: nil))}}}

写入保存一个Key的实现


class CKSaveValueHandler: CKCommandHandlerProtocol {var COMMAND_NAME: CKCommandType = .SAVE_VALUEfunc evaluateExecution(command: String) -> Bool {return CKCommandType(rawValue: command) == COMMAND_NAME}func handle(command: String, arguments: Dictionary<String, Any>, result: @escaping FlutterResult) {if (!evaluateExecution(command: command)) {return}if let key = arguments["key"] as? String, let value = arguments["value"] as? String{let store = NSUbiquitousKeyValueStore.defaultstore.set(value, forKey: key)result(true)} else {result(FlutterError.init(code: "Error", message: "Cannot pass key and value parameter", details: nil))}}}

多设备实时刷新的实现

这里其实实现一下原生的通知监听，返回到Flutter就行，代码如下。

let keyValueStore = NSUbiquitousKeyValueStore.default// 监听数据变化NotificationCenter.default.addObserver(self, selector: #selector(keyValueStoreDidChange), name: NSUbiquitousKeyValueStore.didChangeExternallyNotification, object: keyValueStore)keyValueStore.synchronize()@objc func keyValueStoreDidChange(notification: Notification) {// 处理数据变化if let userInfo = notification.userInfo as? [String: Any],let reasonForChange = userInfo[NSUbiquitousKeyValueStoreChangeReasonKey] as? NSNumber {var reason = -1reason = reasonForChange.intValueif (reason == NSUbiquitousKeyValueStoreServerChange || reason == NSUbiquitousKeyValueStoreInitialSyncChange) {guard let changedKeys = userInfo[NSUbiquitousKeyValueStoreChangedKeysKey] as? [String] else {return}let store = NSUbiquitousKeyValueStore.defaultfor key in changedKeys {let value = store.object(forKey: key)self.channel?.invokeMethod("icloud_key_update", arguments: [key:value])}}}}

Plugin Channel通讯的处理

上面一个一个的协议实现完毕，我们只需要扔到Flutter Plugin handle的协议方法里就可。代码如下


public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {let callArguments: Dictionary<String, Any> = call.arguments as! Dictionary<String, Any>CKGetValueHandler().handle(command: call.method, arguments: callArguments, result: result)CKSaveValueHandler().handle(command: call.method, arguments: callArguments, result: result)CKDeleteValueHandler().handle(command: call.method, arguments: callArguments, result: result)}

就这样一个支持跨苹果全家桶同步持久化Key Value数据的Flutter插件就完全了，是不是很简单呢？

用法

首先我们要在iOS或Mac项目开启iCloud Key Value Storge 服务

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然后导入icloud_kv_storage享受它吧～

flutter pub add icloud_kv_storagedependencies:icloud_kv_storage: ^0.0.1

简单写法如下

import 'package:icloud_kv_storage/icloud_kv_storage.dart';var iCloudStorage = CKKVStorage();

Update A Key

void _incrementCounter() {setState(() {_counter++;iCloudStorage.writeString(key: key, value: _counter.toString());});}

Read A Key

iCloudStorage.getString('k_storage_count').then((value) {if (value != null) {setState(() {_counter = int.parse(value);});}});

Delete A Key

void _clearCounter() {setState(() {_counter = 0;iCloudStorage.delete(key);});}

实时刷新CallBack

iCloudStorage.onCloudKitKVUpdateCallBack(onCallBack: (kvMap) {print('receive icloud_key_update map $kvMap');//if receive remove key will rec {flutter.k_storage_count: null}//if receive update key will rec {flutter.k_storage_count: 1}//because have prefix flutter. so need use my method to get real key.var key = iCloudStorage.getRealKey('k_storage_count');if (kvMap.containsKey(key)) {String? value = kvMap[key];setState(() {if (value != null) {_counter =int.parse(kvMap[iCloudStorage.getRealKey('k_storage_count')]);} else {_counter = 0;}});}},);