ios - 如何实现 Firebase Listener 来观察数据库中的实时变化

Question

我在理解如何实现监听器以便我可以观察数据库中的更改并将它们实时反射(reflect)到 TableView 时遇到问题。我想观察 isOnline 和 isHorizo​​ntal 的变化，根据该变化我将更改标签值以及图像值。这是我的代码:

var userInfoArray : [UserModel] = [UserModel]()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
      // readData()
        tableView.dataSource = self
        tableView.delegate = self
        self.tableView.rowHeight = 70
       retrieveUserInfo()

    }


    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
//        print(emailModified.count)
        return userInfoArray.count

    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "tableViewCell", for: indexPath) as! TableViewCell
        cell.userLbl.text = "User \([userInfoArray[indexPath.row].email].count)"
        if userInfoArray[indexPath.row].isHorizontal == true {
            cell.messageLbl.text = "I am Horizontal"
        } else {
            cell.messageLbl.text = ""
        }

        if userInfoArray[indexPath.row].isOnline == true {

            cell.onlineImage.image = UIImage(named: "online")
        }else {
            cell.onlineImage.image = UIImage(named: "offline")
        }
        return cell

    }
     func retrieveUserInfo() {
     Database.database().reference().child("new user").observeSingleEvent(of: .value) { (snapshot) in
        for child in snapshot.children.allObjects as! [DataSnapshot] {
            print(child.children)
        // this will iterate through all children in snapshot at at path specified.
            if let userList = child.value as? Dictionary <String,Any> {

                    let email = userList["email"]
                    print(email)
                    let onlineStatus = userList["isOnline"] as! Any
                    let horizontalStatus = userList["isHorizontal"] as! Any

                    let list = UserModel()
                    list.email = email as? String ?? "nil"
                    print(list.email)
                    list.isHorizontal = horizontalStatus  as! Bool
                    list.isOnline = onlineStatus  as!   Bool

                    self.userInfoArray.append(list)
                    print(self.userInfoArray)

            }
            self.tableView.reloadData()
        }
        }

Answer 1

我找到了解决方案...

func retrieveUserInfo() {

     Database.database().reference().child("new user").observe(of: 
     DataSnapShot.value) { (snapshot) in
        for child in snapshot.children.allObjects as! [DataSnapshot] {
            print(child.children)
        // this will iterate through all children in snapshot at at path specified.
            if let userList = child.value as? Dictionary <String,Any> {

                    let email = userList["email"]
                    print(email)
                    let onlineStatus = userList["isOnline"] as! Any
                    let horizontalStatus = userList["isHorizontal"] as! Any

                    let list = UserModel()
                    list.email = email as? String ?? "nil"
                    print(list.email)
                    list.isHorizontal = horizontalStatus  as! Bool
                    list.isOnline = onlineStatus  as!   Bool

                    self.userInfoArray.append(list)
                    print(self.userInfoArray)

            }
            self.tableView.reloadData()
        }
        }

我之前正在观察一个事件，当数据库中发生更改时，观察者(DataSnapShot.value)会通知观察者。