Swift-类型'User'的值没有成员'uid'错误Firebase

Question

如何解决此错误。升级到Firebase 5后，我开始出现错误。我该如何解决？在此先感谢您的帮助。下面是出现错误的代码的屏幕截图，您可以在swift文件中找到所有代码。

错误代码：

完整代码：

import UIKit

class CommentViewController: UIViewController {

    @IBOutlet weak var commentTextField: UITextField!
    @IBOutlet weak var sendButton: UIButton!
    @IBOutlet weak var tableView: UITableView!
    @IBOutlet weak var constraintToBottom: NSLayoutConstraint!

    var postId: String!
    var comments = [Comment]()
    var users = [User]()
    override func viewDidLoad() {
        super.viewDidLoad()
        title = "Yorum"
        tableView.dataSource = self
        tableView.estimatedRowHeight = 77
        tableView.rowHeight = UITableViewAutomaticDimension
        empty()
        handleTextField()
        loadComments()

        NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide(_:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        view.endEditing(true)
    }

    @objc func keyboardWillShow(_ notification: NSNotification) {
        print(notification)
        let keyboardFrame = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as AnyObject).cgRectValue
        UIView.animate(withDuration: 0.3) {
            self.constraintToBottom.constant = keyboardFrame!.height
            self.view.layoutIfNeeded()

        }
    }
    @objc func keyboardWillHide(_ notification: NSNotification) {
        UIView.animate(withDuration: 0.3) {
            self.constraintToBottom.constant = 0
            self.view.layoutIfNeeded()

        }
    }


    func loadComments() {
         Api.Post_Comment.REF_POST_COMMENTS.child(self.postId).observe(.childAdded, with: {
            snapshot in
            Api.Comment.observeComments(withPostId: snapshot.key, completion: {
                comment in
                self.fetchUser(uid: comment.uid!, completed: {
                    self.comments.append(comment)
                    self.tableView.reloadData()
                })
            })
        })
    }

    func fetchUser(uid: String, completed:  @escaping () -> Void ) {

        Api.User.observeUser(withId: uid, completion: {
            user in
            self.users.append(user)
            completed()
        })
    }

    func handleTextField() {
        commentTextField.addTarget(self, action: #selector(self.textFieldDidChange), for: UIControlEvents.editingChanged)
    }

    @objc func textFieldDidChange() {
        if let commentText = commentTextField.text, !commentText.isEmpty {
            sendButton.setTitleColor(UIColor.black, for: UIControlState.normal)
            sendButton.isEnabled = true
            return
        }
        sendButton.setTitleColor(UIColor.lightGray, for: UIControlState.normal)
        sendButton.isEnabled = false
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.tabBarController?.tabBar.isHidden = true
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        self.tabBarController?.tabBar.isHidden = false
    }


    @IBAction func sendButton_TouchUpInside(_ sender: Any) {

        let commentsReference = Api.Comment.REF_COMMENTS
        let newCommentId = commentsReference.childByAutoId().key
        let newCommentReference = commentsReference.child(newCommentId)
        guard let currentUser = Api.User.CURRENT_USER else  {
            return
        }
        let currentUserId = currentUser.uid
        newCommentReference.setValue(["uid": currentUserId, "commentText": commentTextField.text!], withCompletionBlock: {
            (error, ref) in
            if error != nil {
                ProgressHUD.showError(error!.localizedDescription)
                return
            }
            let postCommentRef = Api.Post_Comment.REF_POST_COMMENTS.child(self.postId).child(newCommentId)
            postCommentRef.setValue(true, withCompletionBlock: { (error, ref) in
                if error != nil {
                    ProgressHUD.showError(error!.localizedDescription)
                    return
                }
            })
            self.empty()
            self.view.endEditing(true)
        })
    }

    func empty() {
        self.commentTextField.text = ""
        self.sendButton.isEnabled = false
        sendButton.setTitleColor(UIColor.lightGray, for: UIControlState.normal)
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "Comment_ProfileSegue" {
            let profileVC = segue.destination as! ProfileUserViewController
            let userId = sender  as! String
            profileVC.userId = userId
        }
    }
}

extension CommentViewController: UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return comments.count
    }
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "CommentCell", for: indexPath) as! CommentTableViewCell
        let comment = comments[indexPath.row]
        let user = users[indexPath.row]
        cell.comment = comment
        cell.user = user
        cell.delegate = self
        return cell
    }
}

extension CommentViewController: CommentTableViewCellDelegate {
    func goToProfileUserVC(userId: String) {
        performSegue(withIdentifier: "Comment_ProfileSegue", sender: userId)
    }
}