ios - 如何获得像 "dictionary.count"返回值这样的全局定义？

Question

我正在尝试从 Firebase 实时数据库中获取特定的用户消息。我想填写 chatLogTableView使用用户消息。我正在使用 fetchCurrentUserMessages() 从 Firebase 获取用户消息数据功能。

在这个函数中:

self.messagesDatas.append(message)

print(self.messagesDatas)

当我尝试打印 self.messagesDatas没关系。但是当 tableview 试图检索 self.messagesDatas.count对于 numberOfRowsInSection我的计数为 0。为什么会这样？

这是我的代码:

import UIKit
import Firebase

class ChatLogCustomCell: UITableViewCell {

    @IBOutlet weak var leftLabel: UILabel!
    @IBOutlet weak var rightLabel: UILabel!

}


class ChatLogViewController: UIViewController,UITableViewDelegate, UITableViewDataSource {

    @IBOutlet weak var chatLogTableView: UITableView!


    @IBOutlet weak var messageTextField: UITextField! // bu kismi elle yazman gerekebilir cunku xcode bu messagetextfield i sanki view in icinde oldugu icin table view icinde algilayamayabilir

    @IBOutlet weak var backButton: UINavigationItem!
    var usersDataFromChatScreen = [User]()
    var selectedUserToIDFromChatScreen = ""
    var isTeacherFromChatScreen = ""

    var messagesDatas = [Message]()
    var messagesDictionary = [String : Message]()


    override func viewDidLoad() {
        super.viewDidLoad()

        chatLogTableView.delegate = self
        chatLogTableView.dataSource = self

    }


    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return messagesDatas.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = chatLogTableView.dequeueReusableCell(withIdentifier: "chatLogCell") as! ChatLogCustomCell

        let message = messagesDatas[indexPath.row]

        cell.leftLabel.text = message.text
        cell.rightLabel.text = message.text

        return cell
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return 80.0
    }

    @IBAction func sendButtonTouchOnInside(_ sender: Any) {
        let ref = Database.database().reference().child("messages")
        let childRef = ref.childByAutoId()

        let toID = selectedUserToIDFromChatScreen

        Auth.auth().addStateDidChangeListener { (auth, user) in
            let fromID = auth.currentUser?.uid

            let values = ["text" : self.messageTextField.text, "toID" : toID, "fromID" : fromID] as [String : Any]

            childRef.updateChildValues(values) { (error, ref) in
                if error != nil {
                    print(error ?? "")
                    return
                }

                guard let messageID = childRef.key else { return }

                let userMessagesRef = Database.database().reference().child("user-messages").child(fromID!).child(messageID)
                userMessagesRef.setValue(1)

                let recipientUserMessagesRef = Database.database().reference().child("user-messages").child(toID).child(messageID)
                recipientUserMessagesRef.setValue(1)
            }
        }



    }

    func fetchCurrentUserMessages() {
            guard let uid = Auth.auth().currentUser?.uid else {
                return
            }

            if self.isTeacherFromChatScreen == "no" {
                let ref = Database.database().reference().child("user-messages").child(uid)

                ref.observe(.childAdded) { (snapshot) in
                    let messageID = snapshot.key
                    let messagesRef = Database.database().reference().child("messages").child(messageID)

                    messagesRef.observeSingleEvent(of: .value) { (snapshot) in
                        guard let dictionary = snapshot.value as? [String: AnyObject] else {
                            return
                        }

                        let message = Message()

                        let toID = dictionary["toID"] as? String ?? "toID not found"
                        let messageText = dictionary["text"] as? String ?? "Text not found"

                        let fromID = dictionary["fromID"] as? String ?? "fromID not found"

                        message.toID = toID
                        message.text = messageText
                        message.fromID = fromID
                        self.messagesDatas.append(message)

                        print(self.messagesDatas.count)

                    }

                }

            }
            else {

            }

        }




}

Answer 1

从服务器获取数据时重新加载表格 View

func fetchCurrentUserMessages() {
            guard let uid = Auth.auth().currentUser?.uid else {
                return
            }

            if self.isTeacherFromChatScreen == "no" {
                let ref = Database.database().reference().child("user-messages").child(uid)

                ref.observe(.childAdded) { (snapshot) in
                    let messageID = snapshot.key
                    let messagesRef = Database.database().reference().child("messages").child(messageID)

                    messagesRef.observeSingleEvent(of: .value) { (snapshot) in
                        guard let dictionary = snapshot.value as? [String: AnyObject] else {
                            return
                        }

                        let message = Message()

                        let toID = dictionary["toID"] as? String ?? "toID not found"
                        let messageText = dictionary["text"] as? String ?? "Text not found"

                        let fromID = dictionary["fromID"] as? String ?? "fromID not found"

                        message.toID = toID
                        message.text = messageText
                        message.fromID = fromID
                        self.messagesDatas.append(message)

                        print(self.messagesDatas.count)
                        DispatchQueue.main.async {
                         chatLogTableView.reloadData()
                         }


                    }

                }

            }
            else {

            }

        }