From Google Firestore, I am fetching modeled user data individually. Once 1 user's data has been completely fetched, a completion handler is executed and the user will be added to a global array of users (self.activeUsers) and then I call reloadData() on my UITableView (self.activeUsersTableView). I noticed users are getting loaded on top of each other and it is not a UI construction issue or auto layout issues. I can tell because when I print out the indexPath.row in cellForRowAt, I notice duplicate prints of the same index. Anybody got an idea as to why? reloadData() is ONLY called in 1 place for this UITableView which is in the body of myCompletionHandler

    private lazy var activeUsersTableView: UITableView = {
        let table = UITableView()
        table.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
        table.dataSource = self
        table.delegate = self
        table.allowsSelection = false

        return table
    }()

override func viewDidLoad() {
        super.viewDidLoad()

        loadActiveUsersTableView()
        fetchActiveUsers()
    } 

    func loadActiveUsersTableView() {
        self.view.addSubview(activeUsersTableView)
        self.activeUsersTableView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate(
            [
                self.activeUsersTableView.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 150),
                self.activeUsersTableView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 30),
                self.activeUsersTableView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -280),
                self.activeUsersTableView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -250),
            ]
        )
    }

    func fetchActiveUsers() {
        let myCompletionHandler: (UserProfile) -> Void = { theUser in
            self.activeUsers.append(theUser)
            self.activeUsersTableView.reloadData()
        }
        self.chatsDocRef!.getDocument { document, error in
            if let error = error as NSError? {
                print("Error getting document: \(error.localizedDescription)")
            }
            else {
                if let document = document {
                    let data = document.data()
                    self.activeUserUIDS = data?["users"] as? [String]
                    for i in 0..<(self.activeUserUIDS?.count ?? 0) {
                        print("Retrieving document for user ID: ", self.activeUserUIDS![i])
                        let userDocRef = Firestore.firestore().collection("users").document(self.activeUserUIDS![i])
                        UserProfile.getUserProfileData(userDocRef, using: myCompletionHandler)
                    }
                }
            }
        }
    }

Here is the cellForRowAt call and followed by that is my output from the print method. I left out the code AFTER the print for better readability (it isn't important in this case)

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        print("The row", indexPath.row)
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
        return cell
    }

OUTPUT: The row 0 The row 0 The row 1 The row 0 The row 1 The row 2 The row 0 The row 1 The row 2 The row 3 The row 0 The row 1 The row 2 The row 3 The row 4 The row 0 The row 1 The row 2 The row 3 The row 4 The row 5 The row 0 The row 1 The row 2 The row 3 The row 4 The row 5 The row 0 The row 1 The row 2 The row 3 The row 4 The row 5 The row 0 The row 1 The row 2 The row 3 The row 4 The row 5

CodePudding user response：

the real root of the problem was the fact I was not using custom cell design and clearing my cells prior to reuse by using prepareForReuse() method. I implemented a custom cell design and this fixed my issue.