サーバーと同期してリアルタイムに更新する画面を実装する

by izumi

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サーバーと同期してリアルタイムに更新する画面を実装する iOSDC2022 @rizumi

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5 アプリの画面更新

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15 リアルタイム更新の実装例

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Cluster, Inc. All Rights Reserved. 18 更新方法1. polling let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { _ in Task { // 差分があれば画面更新 let data = await self.apiClient.fetch() refreshIfNeeded(data) } }

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Cluster, Inc. All Rights Reserved. 24 更新方法2. サイレントPush通知 func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) { // サイレントpush受信 // ここで画面に受信通知をする (e.g. NotificationCenter) } ● Appdelegateで受信時の処理をハンドリング

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Cluster, Inc. All Rights Reserved. 28 import FirebaseDatabase ... // Realtime Database let ref = Database.database().reference() ref.child(“users”).observe(.value, with: { snapshot in let value = snapshot.value // 画面更新 refresh(value) }) 更新方法3. Firebase Realtime Database / Cloud Firestore

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Cluster, Inc. All Rights Reserved. 32 更新方法4. WebSocket class WebSocketEngine: NSObject, URLSessionWebSocketDelegate { private var task: URLSessionWebSocketTask? func connect() { let session = URLSession(configuration: .default, delegate: self, delegateQueue: nil) task = session.webSocketTask(with: .init(string: "ws://example")!) doReceive() task?.resume() } func urlSession(_ session: URLSession, webSocketTask: URLSessionWebSocketTask, didOpenWithProtocol protocol: String?) { // connected } }

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Cluster, Inc. All Rights Reserved. 33 更新方法4. WebSocket private func doReceive() { task?.receive { [weak self] (result) in switch result { case .success(let message): switch message { case .string(let string): // Receive string case .data(let data): // Receive data @unknown default: // error } self?.doReceive() case .failure(let error): // error } } }

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Cluster, Inc. All Rights Reserved. 34 更新方法4. WebSocket func disconnect() { task?.cancel(with: .normalClosure, reason: nil) } func urlSession(_ session: URLSession, webSocketTask: URLSessionWebSocketTask, didCloseWith closeCode: URLSessionWebSocketTask.CloseCode, reason: Data?) { // disconnected }

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Cluster, Inc. All Rights Reserved. 35 更新方法4. WebSocket SwiftのWebSocket library ● Starscream ○ https://github.com/daltoniam/Starscream ● socket.io-client-swift ○ https://github.com/socketio/socket.io-client-swift ● SwiftWebSocket ○ https://github.com/tidwall/SwiftWebSocket

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Cluster, Inc. All Rights Reserved. 37 各手法のpros / cons比較メリットデメリット polling シンプルな実装パフォーマンスが良くない silent push Pushの実装を使いまわせる拡張性が低い Firebase SDKを使った実装がシンプル mBaasの基盤で安定 Firebaseが使えない環境だと利用できない WebSocket 自由度 / 拡張性が高い実装やメンテナンスコストが高い ● 要件 / 仕様と併せて最適なものを選ぶと良い

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38 clusterでの実例

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Cluster, Inc. All Rights Reserved. 44 接続 / 切断の管理 RealtimeSync Manager Auth API WebSocket token connect(token) 以下の状態をRealtimeSyncManagerが管理状態に変化がある度に接続(or 切断)処理を行う・Login状態・inroom / outroom ・Foreground / Background ・エラーなどでの切断

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Cluster, Inc. All Rights Reserved. 46 更新通知の受信 RealtimeSync Manager WebSocket Protocol Buffers Revisions 初回接続時 or データ更新時に送られてくる struct Revisions { var messageRevision: UInt64 var friendRevision: UInt64 var fooRevision: UInt64 var barRevision: UInt64 }

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Cluster, Inc. All Rights Reserved. 47 更新通知の受信 RealtimeSync Manager WebSocket Protocol Buffers Revisions final class RealtimeSyncManager { var revisions: Observable { revisionsRelay.asObservable() } private var revisionsRelay = PublishRelay() // WebSocketからデータ受信毎に呼ぶ private func doReceive(_ data: Data) { // protobufをdecode guard let revisions = try? Revisions(contiguousBytes: data) else { return } revisionsRelay.accept(revisions) } }

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Cluster, Inc. All Rights Reserved. 48 更新通知の受信 RealtimeSync Manager WebSocket FriendSync subscribe Protocol Buffers Revisions final class FriendSync { private var currentRevision: UInt64 private let bag = DisposeBag() init(realtimeSyncManager: RealtimeSyncManager, repository: FriendRepository) { realtimeSyncManager.revisions .subscribe(onNext: { [weak self] revisions in guard let self = self else { return } if self.currentRevision != revisions.friendRevision { self.currentRevision = revisions.friendRevision repository.fetchRequest() } }) .disposed(by: bag) } } Revisionの更新チェック

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Cluster, Inc. All Rights Reserved. 49 更新通知の受信 RealtimeSync Manager WebSocket FriendSync subscribe Revisionの更新チェック Protocol Buffers Revisions FriendAPI Friend Repository fetch Friend ViewModel FriendView subscribe data bind 更新をrequest

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Cluster, Inc. All Rights Reserved. 50 更新通知の受信 RealtimeSync Manager WebSocket FriendSync subscribe Revisionの更新チェック Protocol Buffers Revisions FriendAPI Friend Repository fetch Friend ViewModel FriendView subscribe data bind 更新をrequest 各画面共通の設計

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Cluster, Inc. All Rights Reserved. 51 更新通知の受信 RealtimeSync Manager WebSocket Sync subscribe Revisionの更新チェック Protocol Buffers Revisions API Repository fetch ViewModel View subscribe data bind 更新をrequest 各画面共通の設計新規でリアルタイム更新を追加する場合この部分を新設するだけでOK

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52 UI更新時に考慮するポイント

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Cluster, Inc. All Rights Reserved. 54 差分更新を使う ● DiffableDataSources var snapshot = NSDiffableDataSourceSnapshot() snapshot.appendSections([.section]) snapshot.appendItems(items) dataSource.apply(snapshot)