删除 tableView 单元格并从 firebase 中删除数据

Question

我正在研究社交网络的项目。卡在从 Firebase 数据库中删除用户 cmets 的阶段。要删除特定评论，我需要知道评论 ID，但我不明白如何访问它。非常感谢您对此提供的任何帮助！

Firebase 数据库示例：

评论视图控制器：

class CommentViewController: UIViewController {

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

var postId: String!
var comments = [Comment]()
var users = [User]()

override func viewDidLoad() {
    super.viewDidLoad()
    tableView.dataSource = self
    title = "Comment"
    tableView.estimatedRowHeight = 77
    tableView.rowHeight = UITableView.automaticDimension
    empty()
    handleTextField()
    loadComments()
    
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow(_:)), name: UIResponder.keyboardWillShowNotification, object: nil)
    
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
}

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


@objc func keyboardWillShow(_ notification: NSNotification) {
    let keyboardFrame = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] 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()
    }
}

var comment: Comment?


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: UIControl.Event.editingChanged)
}

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

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
}

func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
    return true
}

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
    if (editingStyle == .delete) {
        

        
        
    }
}

CommentTableViewCell：

class CommentTableViewCell: UITableViewCell {
@IBOutlet weak var profileImageView: UIImageView!
@IBOutlet weak var nameLabel: UILabel!
@IBOutlet weak var commentLabel: UILabel!

var delegate: CommentTableViewCellDelegate?
var comment: Comment? {
    didSet {
        updateView()
    }
}


var user: User? {
    didSet {
        setupUserInfo()
    }
} 

func updateView() {
    commentLabel.text = comment?.commentText
}


func setupUserInfo() {
    nameLabel.text = user?.username
    if let photoUrlString = user?.profileImageUrl {
        let photoUrl = URL(string: photoUrlString)
        profileImageView.sd_setImage(with: photoUrl, placeholderImage: UIImage(named: "photo_placeholder"))
    }
}

override func awakeFromNib() {
    super.awakeFromNib()
    nameLabel.text = ""
    commentLabel.text = ""
    let tapGestureForNameLabel = UITapGestureRecognizer(target: self, action: #selector(self.nameLabel_TouchUpInside))
    nameLabel.addGestureRecognizer(tapGestureForNameLabel)
    nameLabel.isUserInteractionEnabled = true
}

@objc func nameLabel_TouchUpInside() {
    if let id = user?.id {
        delegate?.goToProfileUserVC(userId: id)
    }
}

override func prepareForReuse() {
    super.prepareForReuse()
    profileImageView.image = UIImage(named: "placeholderImg")
}

override func setSelected(_ selected: Bool, animated: Bool) {
    super.setSelected(selected, animated: animated)

    // Configure the view for the selected state
}

评论接口

class CommentApi {
var REF_COMMENTS =  Database.database().reference().child("comments")

func observeComments(withPostId id: String, completion: @escaping (Comment) -> Void) {
    REF_COMMENTS.child(id).observeSingleEvent(of: .value, with: {
        snapshot in
        if let dict = snapshot.value as? [String: Any] {
            let newComment = Comment.transformComment(dict: dict, key: snapshot.key)
            completion(newComment)
        }
    })
}

func observeComment(withId id: String, completion: @escaping (Comment) -> Void) {
    REF_COMMENTS.child(id).observeSingleEvent(of: DataEventType.value, with: {
        snapshot in
        if let dict = snapshot.value as? [String: Any] {
            let comment = Comment.transformComment(dict: dict, key: snapshot.key)
            completion(comment)
        }
    })
}

评论模型：

class Comment {
var commentText: String?
var uid: String?
var id: String?}

 extension Comment {
static func transformComment(dict: [String: Any], key: String) -> Comment {
    let comment = Comment()
    comment.id = key
    comment.commentText = dict["commentText"] as? String
    comment.uid = dict["uid"] as? String
    return comment
}

Answer 1

概括地说，您的 tableView 由 dataSource 支持，通常是一个数组，它是 tableView 中显示的内容的来源。

var userCommentArray = [UserComment]()

您应该从 Firebase 加载数据并将该数据作为 UserComment 对象存储在数组中

class UserComment {
   var firebaseKey = ""
   var commentText = ""
   var uid = ""
}

firebase_key 属性是 Firebase 中节点的键，在截图中显示为-MH_xxxx，commentText 和 uid 是该节点的子数据。

数组中元素的索引匹配 tableView 中显示的内容，因此 row0 匹配数组索引 0，row 1 匹配数组索引 1 等等。

当用户删除第 1 行时，您知道这是数组中的索引 1。读取对象，获取它的 firebaseKey，然后将其从 firebase 中删除，相应地更新数组，然后重新加载您的 UI。

有关该过程的详细信息，请参阅我对您的 Other Question 的回答。