数组索引从Firebase

Question

我在firebase中的节点添加或删除数据时发生错误。在firebase上添加或删除数据时，我得到一个数组索引超出范围的错误。我的数组有两个项目，但tableView认为有三个项目，因此尝试访问一个不存在的值。我无法弄清楚如何防止这种情况发生。对于更多上下文，我使用带有闭包的alertView，该闭包在firebase中执行添加或删除信息。此alertView位于didSelectCellAtIndexPath方法中。在访问数组时，在cellForRowAtIndexPath方法中发生错误user.id = self.bookRequestors[indexPath.row]

以下是我写的一些代码：    `

   alertVC.addAction(PMAlertAction(title: "Approve this users request",            
     style: .default, action: {
        print("Book Approved")
        let user = User()

        user.id = self.bookRequestors[indexPath.row]

        var users = self.userInfoArray[indexPath.row]

        var bookRef = Database.database().reference().child("books").child("-" + self.bookID)

        bookRef.observeSingleEvent(of: .value, with: { (snapshot) in
            var tempDict = snapshot.value as! [String:AnyObject]



            if tempDict["RequestApproved"] == nil || tempDict["RequestApproved"] as! String == "false"{

                //bookRef.updateChildValues(["RequestApproved": "true", "ApprovedRequestor": user.id])
                bookRef.updateChildValues(["RequestApproved": "true", "ApprovedRequestor": user.id], withCompletionBlock: { (error, ref) in

                    let userRef = Database.database().reference().child("users").child(user.id!).child("requestedBooks")
                    // true meaning this book has been approved for this user
                    userRef.updateChildValues(["-" + self.bookID:"true"])
                })

            } else{

                print("Already Approved!")

                 let alertVC = PMAlertController(title: "Sorry?", description: "You Already Approved that book for someone Else", image: UIImage(named: "booksandcoffee.jpg"), style: .alert)

                alertVC.addAction(PMAlertAction(title: "Ok", style: .default))

                self.present(alertVC, animated: true, completion: nil)

            }

        })`

编辑：更多背景代码

 override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "people", for: indexPath) as! RequestTableViewCell

    // Configure the cell...

 var users = self.userInfoArray[indexPath.row]


    var myName = users["name"]
    var myPic = users["profileImageUrl"]


    let user = User()
    print("This is a count: \(self.bookRequestors.count)")

    print ("the index is: \(indexPath)")

  //This is the array throwing the error, but this array is populated from the previous view and is not modified afterwards.
    user.id = self.bookRequestors[indexPath.row]





    cell.userImage?.setRounded()
    cell.userImage.clipsToBounds = true






    let processor = RoundCornerImageProcessor(cornerRadius: 100)

    DispatchQueue.main.async {

        cell.userImage.loadImageUsingCacheWithUrlString(myPic as! String)

    }


    cell.userName.text = myName as! String

        if user.id == approvedRequestorID{
            cell.wasApproved.image = UIImage(named: "icons8-checked_filled.png")
            cell.approvedLabel.text = "You approved to swap with: "
        }


    cell.backgroundColor = .clear

    return cell
}

编辑II：这是我的numberofSections和numberofRowsPerSection方法

 override func numberOfSections(in tableView: UITableView) -> Int {
    // #warning Incomplete implementation, return the number of sections
    return 1
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete implementation, return the number of rows
    return userInfoArray.count
}

编辑III：更新userInfoArray的函数。

 func grabUsers(){
    //print(bookRequestors)
    for requests in bookRequestors{

    let usersRef = Database.database().reference().child("users").child(requests)

        usersRef.observe(.value, with: { (snapshot) in

            var myDict:[String: AnyObject] = [:]

            myDict = snapshot.value as! [String:AnyObject]

            self.userInfoArray.append(myDict)

            self.tableView.reloadData()
        })

    }

}