CollectionView reloadData in moveItemAtIndexPath resulting duplicate image sometimes

Question

• In my app currently we need reordering images in collectionView and the first image of collectionView should reflect on imageView, So here is my implementation

  //MARK: Variable declaration
  
   @IBOutlet var imageViewMain: UIImageView!
   @IBOutlet var collectionViewImages: UICollectionView!
   var listingImages : [UIImage] = [UIImage(named:"demo_advertisement")!, UIImage(named:"camera_black")!, UIImage(named:"twitter-bird-logo")!, UIImage(named:"money-bag")!]
  
   //MARK: DataSource
  
     func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell
    {
  
      let addPhotosCell = collectionView.dequeueReusableCellWithReuseIdentifier("AddPhototsCollectionViewCell", forIndexPath: indexPath) as! AddPhototsCollectionViewCell
      addPhotosCell.imageView.image = listingImages[indexPath.item]
  
      //        if listingImages.count > 0 {
      //            imageViewMain.image = listingImages[0]
      //        }
  
      return addPhotosCell
    }
  
    func collectionView(collectionView: UICollectionView, moveItemAtIndexPath sourceIndexPath: NSIndexPath,toIndexPath destinationIndexPath: NSIndexPath) {
  
      // swap values if sorce and destination
      let src = listingImages[sourceIndexPath.row]
      let dest = listingImages[destinationIndexPath.row]
      listingImages[destinationIndexPath.row] = src
      listingImages[sourceIndexPath.row] = dest        
  
      self.collectionViewImages.performBatchUpdates({
  
          self.collectionViewImages.reloadData()
  
          }, completion: nil)
  
  }
  

What I'm trying to achieve :

• First element of collevtionView should display on imageViewMain
• Reorder the collectionView images (I'm done with this using long tap gesture on ColletionView)

Issue :

If I do

   self.collectionViewImages.reloadData()

in moveItemAtIndexPath while reordering images its showing me duplicate images like

I'm calling reloadData() because I need to set first element of collectionView to imageViewMain in cellForItemAtIndexPath.

My attempt : In case if I don't call reloadData and try to set image to imageViewMain in moveItemAtIndexPath like

    imageViewMain.image = listingImages[0]  

after below lines, it will not reflect properly on imageViewMain.(But in this case reordering of images works perfectly without any duplicate image)

    let src = listingImages[sourceIndexPath.row]
    let dest = listingImages[destinationIndexPath.row]
    listingImages[destinationIndexPath.row] = src
    listingImages[sourceIndexPath.row] = dest    

Can anyone please suggest me what is the proper way to implement this ?

Answer 1

Actually the logic which i was written in

moveItemAtIndexPath

was wrong. Instead of

let src = listingImages[sourceIndexPath.row]
let dest = listingImages[destinationIndexPath.row]
listingImages[destinationIndexPath.row] = src
listingImages[sourceIndexPath.row] = dest  

It should be

let src = listingImages[sourceIndexPath.row]
listingImages.removeAtIndex(sourceIndexPath.row)
listingImages.insert(src, atIndex: destinationIndexPath.row)
collectionViewImages.reloadData()