Swift - Visual constraints not working - swift

Question

I have a scrollView which I instantiate programaticaly. What I want to do is to add constraints so it will look good in both horizontal and vertical orientation. The problem that constraints not working
How it looks vertically - good
How it looks horizontally - not good
Code is following
class FAPhoto: UIViewController, UIScrollViewDelegate {
var imageURLsArray = [String]()
var imageViews:[UIImageView] = []
var arrayOfPhotos = [Photo]()
var scrollView = UIScrollView()
override func viewDidLoad() {
super.viewDidLoad()
scrollView = UIScrollView(frame: self.view.frame)
view.addSubview(scrollView)
scrollView.contentSize = CGSizeMake(view.frame.size.width * CGFloat(arrayOfPhotos.count), scrollView.frame.size.height)
scrollView.pagingEnabled = true
for (var i = 0; i < arrayOfPhotos.count; i++) {
var imageView = UIImageView()
imageView.frame = CGRectMake(CGFloat(i) * view.frame.size.width, scrollView.frame.origin.y, scrollView.frame.size.width, scrollView.frame.size.height)
imageView.contentMode = .ScaleAspectFit
let image = imageView.hnk_setImageFromURL(NSURL(string: arrayOfPhotos[i].url!)!)
scrollView.addSubview(imageView)
}
}
override func viewWillAppear(animated: Bool) {
}
override func viewWillLayoutSubviews() {
let bindings = Dictionary(dictionaryLiteral: ("scrollView", self.scrollView))
let horizontalConstraints =
NSLayoutConstraint.constraintsWithVisualFormat(
"H:|-0-[scrollView]-0-|",
options: [],
metrics: nil,
views: bindings)
self.view.addConstraints(horizontalConstraints)
let verticalConstraints =
NSLayoutConstraint.constraintsWithVisualFormat(
"V:|-0-[scrollView]-0-|",
options: [],
metrics: nil,
views: bindings)
self.view.addConstraints(verticalConstraints)
}
}

Answer 1

The problem is that you set contentSize of scrollView and imageView's frames in viewDidLoad. This is OK for portrait mode, but when view rotates to landscape, it's frame also changes, so you have to update these values accordingly. I think you have 3 opportunities here.
Track rotation events and update contentSize of scrollView and imageView's frames, when view rotates.
Use Autolayout for scrollView. You will not have to calculate contentSize or set imageView's frames, just set constraints once in viewDidLoad. Here you can find some examples https://stackoverflow.com/a/20232911/4757335.
Use UICollectionView instead of UIScrollView. It handles rotation much easier.