Delete tableView cell and remove data from firebase - ios

Question

I'm working on study project of social network. Stuck on the stage of deleting user comments from Firebase database. To delete a specific comment I need to know the comment Id, but I do not understand how to access it. I'm really appreciate any help on this!
Example of Firebase database:
CommentViewController:
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
}
Comment Api
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)
}
})
}
Comment Model:
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

Speaking at a high level, your tableView is backed by a dataSource, typically an array, which is the source for the content displayed in the tableView.
var userCommentArray = [UserComment]()
you should be loading data from Firebase and storing that data in the array as UserComment objects
class UserComment {
var firebaseKey = ""
var commentText = ""
var uid = ""
}
the firebase_key property is the key to the node in Firebase, shown as -MH_xxxx in the screenshot and then the commentText and uid are is the child data of that node.
The indexes of the elements in the array match what's being shown in the tableView, so row0 matches the array index 0, row 1 matches the array index 1 etc.
When the user deletes row 1, you know that's index 1 in the array. read the object, get it's firebaseKey and then delete it from firebase, updating the array accordingly and then reloading your UI.
See my answer to your Other Question for details on that process.