iOS Swift：从Parse.com检索到的图像没有顺序

Question

I have 3 rows in which I have stored images on each row.

While retrieving the images, I am using "orderBy" to get a standard sequence of objects retrieved. Retrieved strings are in sequence but images are out of sequence. Image sequence is changed randomly on each retrieving action. Can anyone tell me how I can match retrieved strings and image sequence? Also, is this the best way to retrieve images with data in parse?

var customer = NSMutableArray()
var customerDetails = NSMutableArray()
var profilePic : Array<UIImage> = []

 var query:PFQuery = PFQuery(className: "Images")
    query.orderByAscending("createdAt")
    query.findObjectsInBackgroundWithBlock{(objects:[AnyObject]?, error: NSError?) -> Void in
        if(error == nil){
            for object in objects as! [PFObject!] {

                var fName = object["customerName"]! as! String
                var fImage = object["customerImage"] as! PFFile
                var fDetail = object["customerDetail"]! as! String

                fImage.getDataInBackgroundWithBlock({
                    (imageData: NSData?, error: NSError?) -> Void in
                    if (error == nil) {
                        var cImages = UIImage(data:imageData!)
                        println(cImages)
                        self.profilePic.append(cImages!)
                    }

                })//getDataInBackgroundWithBlock - end
                self.customer.addObject(fName)
                self.customerDetails.addObject(fDetail)
            }//for - end

            self.tableView.reloadData()
        }

Answer 1

This is likely because you're fethcing the images asynchronously within an already asynchronous block, so that when you append the images to the arrays, this process of downloading the images will always take longer than just fetching the name and detail of the PFObject . In order to circumvent this, you can try to self.customer.addObject(fName) and self.customerDetails.addObjects(fDetail) inside your if error == nil conditional check.

Answer 2

As per @pbush25, I got the code working. Just to help others, I will clearly re write the full working code as below:

var customer = NSMutableArray()
var customerDetails = NSMutableArray()
var profilePic : Array<UIImage> = []

 var query:PFQuery = PFQuery(className: "Images")
    query.orderByAscending("createdAt") // This may or may not work. I still didn't make it work each time I run the code.
    query.findObjectsInBackgroundWithBlock{(objects:[AnyObject]?, error: NSError?) -> Void in
        if(error == nil){
            for object in objects as! [PFObject!] {

            fImage.getDataInBackgroundWithBlock({
                (imageData: NSData?, error: NSError?) -> Void in
                if (error == nil) {
                    var cImages = UIImage(data:imageData!)
                    var fName = object["customerName"]! as! String
                    var fDetail = object["customerDetail"]! as! String

                    self.customer.addObject(fName)
                    self.customerDetails.addObject(fDetail)
                    self.profilePic.append(cImages!)
                }

            })//getDataInBackgroundWithBlock - end

        }//for - end

        self.tableView.reloadData()
    }