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    ###### tags: `第13屆IT邦鐵人賽文章` # 【在 iOS 開發路上的大小事-Day26】透過 Firebase 來管理資料 (Realtime Database 篇) Part2 # 前情提要 昨天已經將環境設定好了,今天要來將新增、讀取、更新、刪除、排序功能實作出來 # 開始實作 ## 設計留言的 Model 我們會需要一個 id 來記錄這是哪一筆留言,方便我們後面來處理 然後還需要記錄留言人的名字以及留言內容跟最後留言時間 所以就可以將這些東西設計成一個 struct 此外,後面我們還有**透過時間來排序留言**的需求 所以我們還需要讓這個 struct 符合 Comparable 的規範,所以 ```swift= struct MessageModel: Comparable { static func < (lhs: MessageModel, rhs: MessageModel) -> Bool { return lhs.time < rhs.time } var id: String var name: String var content: String var time: String } ``` ## 建立變數 宣告兩個變數,一個是資料庫的參考,一個是用來取得 Struct 內容的 ```swift= var databaseRef: DatabaseReference! var messageList = [MessageModel]() ``` ## 要加到 viewDidLoad 裡面的東西 ```swift= override func viewDidLoad() { super.viewDidLoad() databaseRef = Database.database().reference().child("messages") // 這個是用來告訴 Firebase,我們要找的資料庫路徑 messageTableView.register(UINib(nibName: "RealtimeDatabaseCell", bundle: nil), forCellReuseIdentifier: "RealtimeDatabaseCell") // 因為我是用 Xib 設計畫面,所以要註冊一下 messageTableView.delegate = self messageTableView.dataSource = self self.fetchMessageFromFirebase() // 這個後面會用到,先寫著 } ``` ## 要加到 viewWillAppear 裡面的東西 用來監聽目前資料庫內的狀態,可以監聽的狀態有這些 | 事件類型 | 典型用法 | | -------- | -------- | | FIRDataEventTypeChildAdded| 檢索項列表,或監聽項列表中是否添加了新項。該事件將針對每個現有的子項觸發一次,並在每次向指定的路徑添加新的子項時再次觸發。系統將向監聽器傳遞一個包含新子項的數據的快照。| | FIRDataEventTypeChildChanged| 監聽列表中的項是否發生了更改。每次修改子節點時,均會觸發此事件。這包括對子節點的後代所做的任何修改。傳遞給事件監聽器的快照包含子項的更新數據。| | FIRDataEventTypeChildRemoved| 監聽列表中是否有項被移除。移除直接子項將會觸發此事件。傳遞給回調塊的快照包含已移除的子項的數據。| | FIRDataEventTypeChildMoved| 監聽經過排序的列表的項順序是否有更改。只要更新會引發子項重新排序,就會觸發此事件。該事件用於已通過 queryOrderedByChild 或 queryOrderedByValue 排序的數據。| | FIRDataEventTypeValue | 讀取並監聽對路徑中所有內容的更改。| ```swift= override func viewWillAppear(_ animated: Bool) { super.viewWillAppear(animated) databaseRef.observe(.value) { snapshot in if let output = snapshot.value as? [String: Any] { print("目前資料庫內有 \(output.count) 筆留言") } else { print("目前資料庫內沒有留言!") } } } ``` ## 要加到 viewWillDisappear 裡面的東西 有增加監聽就有移除監聽,這樣才不會浪費系統資源~ ```swift= override func viewWillDisappear(_ animated: Bool) { super.viewWillDisappear(animated) databaseRef.removeAllObservers() } ``` ## 要加到送出 Button 的 IBAction 裡面的東西 ```swift= @IBAction func sendMessageToRealtimeDatabase(_ sender: UIButton) { self.sendMessageToFirebase() } // MARK: - 新增留言到 Firebase Realtime Database func sendMessageToFirebase() { let key = databaseRef.childByAutoId().key let message = [ "id": key, "name": messagePeopleTF.text!, "content": messageContentTV.text!, "time": self.getSystemTime() ] self.databaseRef.child("\(String(describing: key!))").setValue(message) CustomFunc.customAlert(title: "留言已送出!", message: "", vc: self, actionHandler: self.fetchMessageFromFirebase) self.messagePeopleTF.text = "" self.messageContentTV.text = "" } ``` ## 從 Realtime Database 裡面讀取 / 抓取資料 ```swift= // MARK: - 從 Firebase Realtime Database 讀取留言 func fetchMessageFromFirebase() { self.databaseRef.observe(.value) { snapshot in if (snapshot.childrenCount > 0) { self.messageList.removeAll() for messages in snapshot.children.allObjects as! [DataSnapshot] { let messageObject = messages.value as? [String: AnyObject] let messageID = messageObject?["id"] let messageName = messageObject?["name"] let messageContent = messageObject?["content"] let messageTime = messageObject?["time"] let message = MessageModel( id: messageID as! String, name: messageName as! String, content: messageContent as! String, time: messageTime as! String ) self.messageList.append(message) } self.messageTableView.reloadData() } else { self.messageList.removeAll() self.messageTableView.reloadData() } } } ``` ## 取得送出留言 / 更新留言的時間 ```swift= func getSystemTime() -> String { let currectDate = Date() let dateFormatter: DateFormatter = DateFormatter() dateFormatter.dateFormat = "YYYY-MM-dd HH:mm:ss" dateFormatter.locale = Locale.ReferenceType.system dateFormatter.timeZone = TimeZone.ReferenceType.system return dateFormatter.string(from: currectDate) } ``` ## 將留言呈現在 TableView 上面 ```swift= extension RealtimeDataBaseVC: UITableViewDelegate, UITableViewDataSource { func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return messageList.count } func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: "RealtimeDatabaseCell", for: indexPath) as! RealtimeDatabaseCell cell.messagePeople.text = messageList[indexPath.row].name cell.messageContent.text = messageList[indexPath.row].content return cell } ``` ## 更新留言 ```swift=+ func tableView(_ tableView: UITableView, leadingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? { let editAction = UIContextualAction(style: .normal, title: "編輯") { action, view, completeHandler in let alertController = UIAlertController(title: "更新留言", message: "", preferredStyle: .alert) alertController.addTextField { textField in textField.text = self.messageList[indexPath.row].name } alertController.addTextField { textField in textField.text = self.messageList[indexPath.row].content } let updateAction = UIAlertAction(title: "更新", style: .default) { action in let updateMessage = [ "id": self.messageList[indexPath.row].id, "name": alertController.textFields?[0].text!, "content": alertController.textFields?[1].text!, "time": self.getSystemTime() ] self.databaseRef.child("\(String(describing: self.messageList[indexPath.row].id))").setValue(updateMessage) CustomFunc.customAlert(title: "留言更新成功!", message: "", vc: self, actionHandler: nil) } let cancelAction = UIAlertAction(title: "取消", style: .cancel, handler: nil) alertController.addAction(updateAction) alertController.addAction(cancelAction) self.present(alertController, animated: true) completeHandler(true) } let leadingSwipeAction = UISwipeActionsConfiguration(actions: [editAction]) editAction.backgroundColor = UIColor(red: 0.0/255.0, green: 127.0/255.0, blue: 255.0/255.0, alpha: 1.0) return leadingSwipeAction } ``` ## 刪除留言 ```swift=+ func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? { let deleteAction = UIContextualAction(style: .destructive, title: "刪除") { action, view, completeHandler in self.databaseRef.child(self.messageList[indexPath.row].id).setValue(nil) completeHandler(true) } let trailingSwipeAction = UISwipeActionsConfiguration(actions: [deleteAction]) return trailingSwipeAction } } ``` ## 要加到排序留言 Button 的 IBAction 裡面的東西 ```swift= // MARK: - 留言排序 @IBAction func sortMessage(_ sender: UIButton) { self.sortMessageFromFirebase() } enum sortMode { case defaultSort // 預設排序 (從新到舊) case fromNewToOldSort // 從新到舊 case fromOldToNewSort // 從舊到新 } func sortMessageFromFirebase() { let alertController = UIAlertController(title: "請選擇留言排序方式", message: "排序方式為送出/更新留言的時間早晚", preferredStyle: .actionSheet) let defaultAction = UIAlertAction(title: "預設排序", style: .default) { action in self.sortMessageList(sortMode: .defaultSort) } let fromNewToOldAction = UIAlertAction(title: "從新到舊", style: .default) { action in self.sortMessageList(sortMode: .fromNewToOldSort) } let fromOldToNewAction = UIAlertAction(title: "從舊到新", style: .default) { action in self.sortMessageList(sortMode: .fromOldToNewSort) } let closeAction = UIAlertAction(title: "關閉", style: .cancel, handler: nil) alertController.addAction(defaultAction) alertController.addAction(fromNewToOldAction) alertController.addAction(fromOldToNewAction) alertController.addAction(closeAction) self.present(alertController, animated: true) } func sortMessageList(sortMode: sortMode) { if (sortMode == .defaultSort || sortMode == .fromNewToOldSort) { self.messageList.sort(by: >) } else if (sortMode == .fromOldToNewSort) { self.messageList.sort(by: <) } self.messageTableView.reloadData() } ``` # 成果 {%youtube ydXUzSKxi_U %} 本篇的範例程式碼: 1. MessageModel.swift:[Github](https://github.com/leoho0722/IT2021/blob/main/Day15~Day22%E3%80%81Day24~Day28/CocoaPodsDemo/CocoaPodsDemo/Model/MessageModel.swift) 2. RealtimeDataBaseVC.swift:[Github](https://github.com/leoho0722/IT2021/blob/main/Day15~Day22%E3%80%81Day24~Day28/CocoaPodsDemo/CocoaPodsDemo/FirebaseVC/RealtimeDatabaseVC/RealtimeDataBaseVC.swift)

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