Swift How to pan UIImage in UiImageView? - swift3

Question

I have a simple test application and I want to pan an image inside its view. It will not pan or zoom and I can't see what's wrong with my code.
I have followed this tutorial but implemented it in code. I've made the image width the same as the height so I can pan without necessarily zooming.
Here is my code
import UIKit
class ViewController: UIViewController, UIScrollViewDelegate {
let scrollView: UIScrollView = {
let scrollView = UIScrollView()
return scrollView
}()
let zoomImageView: UIImageView = {
let imageView = UIImageView()
imageView.isUserInteractionEnabled = true
imageView.clipsToBounds = true
imageView.contentMode = .scaleAspectFill
imageView.image = #imageLiteral(resourceName: "lighthouse")
return imageView
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
let screenSize = UIScreen.main.bounds
let screenHeight = screenSize.height
scrollView.frame = CGRect(x:0, y:0, width: screenHeight, height: screenHeight)
scrollView.delegate = self
scrollView.minimumZoomScale = 1.0
scrollView.maximumZoomScale = 3.0
zoomImageView.frame = CGRect(x:0, y:0, width: screenHeight, height: screenHeight)
scrollView.addSubview(self.zoomImageView)
view.addSubview(scrollView)
}
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return zoomImageView
}
}

Answer 1

Search in your code for the term contentSize. You don't see it, do you? But the most fundamental fact about how a scroll view works is this: a scroll view without a contentSize cannot scroll (i.e. "pan" as you put it). In particular, it must have a content size larger than its own bounds size in order to be able to scroll along that axis (height or width, or both). Otherwise, there is nothing to scroll.