Cannot Zoom UIImageView - ios

Question

I am new to swift.
I am doing an exercise from an app development book. I am trying to create an UIImageView and put a image in it, but I can not zoom the image in. There is something wrong in my code, but I don't know what is going on.
import UIKit
class ViewController: UIViewController, UIScrollViewDelegate {
#IBOutlet weak var image: UIImageView!
#IBOutlet weak var scroll: UIScrollView!
override func viewDidLoad() {
super.viewDidLoad()
scroll.delegate = ViewController()
updateZoomFor(size:view.bounds.size)
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
private func viewForZooming(in scrollView: UIScrollView) -> UIImageView{
return image
}
func updateZoomFor(size:CGSize){
let widthScale = size.width / image.bounds.width
let heightScale = size.height / image.bounds.height
let scale = min(widthScale, heightScale)
scroll.minimumZoomScale = scale
}
}

Answer 1

First, set scroll.delegate = self as suggested by 3stud1ant3.
Second, you need to match the definition of theUIScrollViewDelegate method:
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return image
}
Make sure you set the zoom scale in updateZoomFor as well: scroll.zoomScale = scale.
Also you need to implement this:
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
updateZoomFor(size: view.bounds.size)
}
func scrollViewDidZoom(_ scrollView: UIScrollView) {
updateConstraintsForSize(view.bounds.size)
}
fileprivate func updateConstraintsForSize(_ size: CGSize) {
let yOffset = max(0, (size.height - imageView.frame.height) / 2)
imageViewTopConstraint.constant = yOffset
imageViewBottomConstraint.constant = yOffset
let xOffset = max(0, (size.width - imageView.frame.width) / 2)
imageViewLeadingConstraint.constant = xOffset
imageViewTrailingConstraint.constant = xOffset
view.layoutIfNeeded()
}