swift - 查询中的查询不附加 Swift/Parse

Question

我希望有人能提供帮助，因为这可能是一个简单的问题，但我在查询中的 Parse 查询打印了我正在寻找的对象，但无法将它附加到我需要它的数组中以在 UITableView 中检索它。

当我将单元格中的查询结果出列时，错误是“ fatal error :索引超出范围”。

代码如下:

导入 UIKit导入解析进口 bolt

类 MessagesTableVC: UITableViewController {

var usernames = [String]()
var sentDate = [NSDate]()
var details = [String]()
var userImage = [PFFile]()


@IBAction func backToProfile(sender: AnyObject) {
    self.performSegueWithIdentifier("messagesToProfile", sender: self)
}


override func viewDidLoad() {
    super.viewDidLoad()

    let messagesQuery = PFQuery(className: "Messages")
    messagesQuery.whereKey("recipientId", equalTo: PFUser.currentUser()!.objectId!)
    messagesQuery.includeKey("senderId")
    messagesQuery.orderByDescending("createdAt")
    messagesQuery.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in

        if error != nil {
            print(error)
        }

        if error == nil {

            if let objects = objects {

                self.usernames.removeAll(keepCapacity: true)
                self.sentDate.removeAll(keepCapacity: true)
                self.details.removeAll(keepCapacity: true)
                self.userImage.removeAll(keepCapacity: true)

                for object in objects {

                    self.sentDate.append(object.createdAt! as NSDate)

                    if (object["item"] != nil) {
                    self.details.append(object["item"] as! String)
                    } else {
                    self.details.append(object["request"] as! String)
                    }

                    let senderObject = (object["senderId"] as! PFUser)
                    let senderId = (senderObject.objectId! as String)

                    print(senderId)

                    // Query for sender info
                    let userQuery = PFUser.query()
                    userQuery?.whereKey("objectId", equalTo: senderId)
                    userQuery?.getFirstObjectInBackgroundWithBlock({ (object, error) in

                        self.usernames.append((object!["username"] as! String))

                        //self.userImage.append(object!["profilePicture"] as! PFFile)

                    })




                }

                dispatch_async(dispatch_get_main_queue()) {
                    self.tableView.reloadData()
                    //self.search.resignFirstResponder()
                }
            }


    }
    })

    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()
}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


// MARK: - Table view data source

override func numberOfSectionsInTableView(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 sentDate.count
}


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("messageCell", forIndexPath: indexPath) as! MessageTableViewCell

    //print(usernames[indexPath.row])
    cell.senderUsername.text = usernames[indexPath.row]
    cell.itemOrPreview.text = details[indexPath.row]

    let date = sentDate[indexPath.row]
    let formatter = NSDateFormatter()
    formatter.dateStyle = NSDateFormatterStyle.LongStyle
    formatter.timeStyle = .ShortStyle
    let dateString = formatter.stringFromDate(date)
    cell.sentDate.text = dateString


    //userImage[indexPath.row].getDataInBackgroundWithBlock { (data, error) in
      //  if let downloadedItemImage = UIImage(data: data!) {
        //    cell.senderImage?.image = downloadedItemImage
        //}
    //}


    return cell
}

override func viewWillAppear(animated: Bool) {
    tableView.reloadData()
}

Answer 1

正如我猜测的那样，您可能会在 sentDate 和 usernames 中得到不一致的元素数量，因为您通过异步 附加到 usernames getFirstObjectInBackgroundWithBlock 方法，因此，当您在 tableView 上调用 reloadData 时，所有用户名可能尚未添加到 usernames。当您的 tableView 回调触发时，usernames 中的项目可能比 sentDate 中的项目少，而在 numberOfItems 中您返回 sentDate 中的项目数。

为了修复您需要首先重构您的代码，它有很多地方可能会出错。我不会给出任何具体建议，但看起来，您可能希望在重新加载 tableView 之前等待所有数据。