单元格图像显示无序，为什么会发生这种情况？

Question

我正在构建一个图像提要，其中包括一个图像，后跟一个表格视图内的用户名标签。出于某种原因，单元格图像与正确的用户名不匹配。似乎图像的下载顺序与用户名不同，但事实并非如此。请帮忙！

编辑：在进行一些控制台日志记录后，我看到图像已下载并附加到图像数组中，其顺序与用户名不同。但我不知道为什么，也不知道如何解决。

import UIKit

class TrendingChallengeTableViewCell: UITableViewCell {


    @IBOutlet var postImage: UIImageView!

    @IBOutlet var postComment: UILabel!


    override func prepareForReuse() {
        super.prepareForReuse()

        self.postImage.image = nil
        self.postComment.text = ""
    }
}



import UIKit
import Parse

var pressedChallenge: String?

class TrendingChallengeTableViewController: UITableViewController {

    var images = [PFFile]()
    var usernames = [String]()



    override func viewDidLoad() {
        super.viewDidLoad()

        navigationItem.hidesBackButton = true

        let query = PFQuery(className: "Post")
        query.whereKey("imageComment", equalTo: pressedChallenge!)
        query.findObjectsInBackgroundWithBlock { (object, error) -> Void in

            self.usernames.removeAll(keepCapacity: true)
            self.images.removeAll(keepCapacity: true)

            if let object = object {
                for images in object {
                    self.images.append(images["imageFile"] as! PFFile)

                    let userQuery = PFUser.query()

                    userQuery?.whereKey("_id", equalTo: images["userId"])
                    userQuery?.findObjectsInBackgroundWithBlock({ (object, error) -> Void in
                        if let object = object {
                            for user in object {
                                self.usernames.append(user["username"] as! String)
                                self.tableView.reloadData()
                            }
                        }
                    })


                }
            }
        }

    }

    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 usernames.count
    }


    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let trendCell = tableView.dequeueReusableCellWithIdentifier("trendingCell", forIndexPath: indexPath) as! TrendingChallengeTableViewCell

         trendCell.postComment.text = "\(usernames[indexPath.row]) completed the \(pressedChallenge!) challenge!"

        images[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
            if let downloadedImage = UIImage(data: data!) {
              trendCell.postImage.image = downloadedImage
            }
        }



        return trendCell
    }


}

Answer 1

在获取对象之前尝试告诉您的两个查询以特定方式排序，即：

let query = PFQuery(className: "Post")
query.whereKey("imageComment", equalTo: pressedChallenge!)
query.orderByDescending("createdAt")
query.findObjectsInBackgroundWithBlock { (object, error) -> Void in
    //etc
}

对第二个查询也这样做。