Image and scrollView rendering making my tableview choppy - ios

Question

There may be no good solution for my problem, but I want to ask just in case.
I have a tableview in which each cell contains a horizontal scrollview of variable width. The width of each cell's scrollview depends on the number and sizes of the images for that cell. Everything works pretty well, but the tableview scrolls less smoothly than it could. I'm using Parse to retrieve the images (and pfquertableviewcontroller), but this question should apply to tableviews in general.
Here is my tableview code:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath, object: PFObject?) -> PFTableViewCell? {
if var cell:MainFeedTableViewCell? = tableView.dequeueReusableCellWithIdentifier(self.cellIdentifier) as? MainFeedTableViewCell{
if(cell == nil) {
cell = NSBundle.mainBundle().loadNibNamed("MainFeedTableViewCell", owner: self, options: nil)[0] as? MainFeedTableViewCell
}
cell?.parseObject = object
return cell
}
}
override func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
if let c = (cell as? MainFeedTableViewCell){
c.setUpObject()//this is where images are set
}
}
override func tableView(tableView: UITableView, didEndDisplayingCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
if let c = (cell as? MainFeedTableViewCell){
c.resetObject() //this sets most of the properties to nil
}
}
And here is the function in my cell where images are set
func setUpObject(){
//I left out several lines of code where label text is set from the parseObject that is set when the cell is created
//setting images **problems here**
if let numImages = self.parseObject?["numImages"] as? Int{
self.newWidth1 = self.parseObject?["width1"] as? CGFloat
self.newWidth2 = self.parseObject?["width2"] as? CGFloat
self.newWidth3 = self.parseObject?["width3"] as? CGFloat
self.newWidth4 = self.parseObject?["width4"] as? CGFloat
self.newWidth5 = self.parseObject?["width5"] as? CGFloat
if numImages == 1{
self.containerView = UIView(frame: CGRect(x: self.scrollView.frame.minX, y: self.scrollView.bounds.minY - 90, width: self.scrollView.frame.width, height: self.scrollView.frame.height))
self.image1 = PFImageView(frame: CGRect(x: self.scrollView.frame.minX , y: self.scrollView.frame.minY, width: self.scrollView.frame.width, height: self.scrollView.frame.height))
self.image1?.contentMode = UIViewContentMode.ScaleAspectFit
self.image1!.file = self.parseObject?["image"] as? PFFile
self.image1!.loadInBackground()
self.containerView!.addSubview(self.image1!)
self.scrollView.contentSize = self.containerView!.bounds.size
self.scrollView.addSubview(self.containerView!)
}
else if numImages == 2{
if self.newWidth1 + self.newWidth2 < self.scrollView.frame.width{
self.containerView = UIView(frame: CGRect(x: self.scrollView.frame.midX - (self.newWidth1 + self.newWidth2)/2, y: self.scrollView.bounds.minY - 90, width: (self.newWidth1 + self.newWidth2), height: self.scrollView.frame.height))
}
else{
self.containerView = UIView(frame: CGRect(x: self.scrollView.frame.minX, y: self.scrollView.bounds.minY - 90, width: (self.newWidth1 + self.newWidth2), height: self.scrollView.frame.height))
}
self.image1 = PFImageView(frame: CGRect(x: self.scrollView.frame.minX , y: self.scrollView.frame.minY, width: self.newWidth1, height: self.scrollView.frame.height))
self.image1!.file = self.parseObject?["image"] as? PFFile
self.image1!.loadInBackground()
self.containerView!.addSubview(self.image1!)
self.image2 = PFImageView(frame: CGRect(x: (self.scrollView.frame.minX + self.newWidth1), y: self.scrollView.frame.minY, width: self.newWidth2, height: self.scrollView.frame.height))
self.image2!.file = self.parseObject?["image2"] as? PFFile
self.image2!.loadInBackground()
self.containerView!.addSubview(self.image2!)
self.subLayer = CALayer()
self.subLayer.backgroundColor = UIColor.whiteColor().CGColor
self.subLayer.frame = CGRect(x: self.newWidth1, y: self.scrollView.frame.minY, width: 1, height: self.scrollView.frame.height)
self.containerView!.layer.addSublayer(self.subLayer)
self.scrollView.contentSize = self.containerView!.bounds.size
self.scrollView.addSubview(self.containerView!)
}
//repeat similar code for cases where there are 3, 4, or 5 images
There might be a fundamental issue with dynamically adjusting the size of the scrollview and adding it to superview just in time, but I'm trying to follow the design mockup that my designer gave me.
Here is what the scrollview on the cell looks like (with each image in the scrollview separated by a thin white line)

Answer 1

Remove your willDisplayCell and didEndDisplayingCell. That will fire as you scroll and your setUpObject code, while not huge, will block the main thread slightly. Instead move setUpObject() to right before returning the cell in cellForRowAtIndexPath.
Depending on how many rows you have and performance requirements you could also adjust the viewController to download all of the images ahead of time and pass them to the cell instead of loading them inside the cell.