Parse getDataInBackgroundWithBlock is not sorted in order

Question

I am extracting a string, NSDate and PFFile from my Parse class to populate the collection view cells

All cells are loaded with the image, date, information correctly. Information and date are ordered correctly (in ascending date). But from time to time, when I create some of the images, you will be in a different cell. I really scratch my head with this. I guess this has something to do with how I call mixPhoto.getDataInBackgroundWithBlock ({

I tried using dispatch_async (dispatch_get_main_queue ())

Still no luck ... Here is my code, who has any ideas?

@IBOutlet weak var collectionView1: UICollectionView!


var mixPhotoArray : Array<UIImage> = []
var mixInfoArray: Array <String> = []
var mixDateArray: Array <NSDate> = []

override func viewDidLoad() {
    super.viewDidLoad()
    collectionView1.delegate = self;
    collectionView1.dataSource = self;

    self.queryParseMethod()
    self.getImageData()

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

    // Do any additional setup after loading the view.
}


func getImageData() {
    var query = PFQuery(className: "musicMixes")
    query.orderByAscending("date")
    query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]!, error: NSError!) -> Void in
    for object in objects {


    let mixPhoto = object["mixPhoto"] as PFFile

        mixPhoto.getDataInBackgroundWithBlock({
            (imageData: NSData!, error: NSError!) -> Void in
            if (error == nil) {
                dispatch_async(dispatch_get_main_queue()) {
                    let image = UIImage(data:imageData)
                    //image object implementation
                    self.mixPhotoArray.append(image!)
                    println(self.mixPhotoArray[0])
                    self.collectionView1.reloadData()

                }
            }
            else {
                println("error!!")
            }

        })//getDataInBackgroundWithBlock - end

        }



    }//for - end

}

    func queryParseMethod() {

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


    let mixPhoto = object["mixPhoto"] as PFFile




        let mixInfo = object["info"] as String
        let dateForText = object["date"] as NSDate


        //self.collectionView1.reloadData()

            self.mixDateArray.append(dateForText)
            self.mixInfoArray.append(mixInfo)
            self.collectionView1.reloadData()


                }//for - end
        }
        }
} // end of queryParseMethod


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()




        }



/*
// MARK: - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

// MARK: UICollectionViewDataSource

 func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
    //#warning Incomplete method implementation -- Return the number of sections
    return 1
}


 func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    //#warning Incomplete method implementation -- Return the number of items in the section
     println("I have \(mixPhotoArray.count) Images")
    return mixInfoArray.count


}

  //func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
  func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    let cell:StreamCollectionViewCell = collectionView1.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as StreamCollectionViewCell

   cell.mixImage.image = mixPhotoArray[indexPath.item]
    cell.infoLabel.text = mixInfoArray[indexPath.item]

    // NSDate array into cell
    var dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd"
   cell.mixDateLabel.text = dateFormatter.stringFromDate(mixDateArray[indexPath.item])






     return cell
}

Answer 1

Wain, , , , , . , , , :

// Declare your mixPhotoArray such that it can store optionals
var mixPhotoArray : Array<UIImage?> = []

func getImageData() {

    var query = PFQuery(className: "musicMixes")
    query.orderByAscending("date")
    query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]!, error: NSError!) -> Void in
        // Initialize your array to contain all nil objects as
        // placeholders for your images
        self.mixPhotoArray = [UIImage?](count: objects.count, repeatedValue: nil)
        for i in 0...objects.count - 1 {

            let object: AnyObject = objects[i]
            let mixPhoto = object["mixPhoto"] as PFFile

            mixPhoto.getDataInBackgroundWithBlock({
                (imageData: NSData!, error: NSError!) -> Void in
                if (error == nil) {
                    dispatch_async(dispatch_get_main_queue()) {
                        let image = UIImage(data:imageData)
                        // Replace the image with its nil placeholder
                        // and do so using the loop current index
                        self.mixPhotoArray[i] = image
                        println(self.mixPhotoArray[i])
                        self.collectionView1.reloadData()
                    }
                }
                else {
                    println("error!!")
                }

            })

        }

    }

}

collectionView:cellForItemAtIndexPath , :

if mixPhotoArray[indexPath.item] != nil {
    cell.mixImage.image = mixPhotoArray[indexPath.item]
}

Answer 2

2 , mixPhotoArray mixInfoArray, , . , . 4 , .

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