Unable to scroll image using scroll view in swift

Question

I am facing this weird problem with scroll view in swift, The image does not scroll even after defining scroll view in the file, I have also added zooming and it worked fine. Please help me with this https://pastebin.com/1uC3fqHG

import UIKit

class ImageViewController: UIViewController
{
    var imageURL: URL? {
        didSet {
            image = nil
            if view.window != nil {
                fetchImage()
            }
        }
    }

    private func fetchImage() {
        if let url = imageURL {
            let urlContents = try? Data(contentsOf: url)
            if let imageData = urlContents {
                image = UIImage(data: imageData)
            }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(imageView)
        imageURL = URL(string: "http://www.lamborghini.com/en-en/sites/en-en/files/DAM/lamborghini/share%20img/huracan-coupe-facebook-og.jpg")
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        if image == nil {
            fetchImage()
        }

    }

    @IBOutlet weak var scrollView: UIScrollView! {
        didSet {

            scrollView.delegate = self
            scrollView.minimumZoomScale = 0.03
            scrollView.maximumZoomScale = 2.0
            scrollView.contentSize = imageView.frame.size
            scrollView.addSubview(imageView)
        }
    }


    fileprivate var imageView = UIImageView()

    private var image: UIImage? {
        get{
            return imageView.image
        }
        set{
            imageView.image = newValue
            imageView.sizeToFit()
            scrollView?.contentSize = imageView.frame.size
        }
    }
}

extension ImageViewController: UIScrollViewDelegate
{
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView
    }
}

Answer 1

You should be updating the content size and update the image view constraints Checkout this tutorial

Answer 2

the problem is that you are adding the image to the view in viewDidLoad(). Remove view.addSubview(imageView) from the viewDidLoad() and all will be working perfectly. Code will become as follows

import UIKit

class ImageViewController: UIViewController
{
    var imageURL: URL? {
        didSet {
            image = nil
            if view.window != nil {
                fetchImage()
            }
        }
    }

    private func fetchImage() {
        if let url = imageURL {
            let urlContents = try? Data(contentsOf: url)
            if let imageData = urlContents {
                image = UIImage(data: imageData)
            }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        imageURL = URL(string: "http://www.lamborghini.com/en-en/sites/en-en/files/DAM/lamborghini/share%20img/huracan-coupe-facebook-og.jpg")
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        if image == nil {
            fetchImage()
        }

    }

    @IBOutlet weak var scrollView: UIScrollView! {
        didSet {

            scrollView.delegate = self
            scrollView.minimumZoomScale = 0.03
            scrollView.maximumZoomScale = 2.0
            scrollView.contentSize = imageView.frame.size
            scrollView.addSubview(imageView)
        }
    }


    fileprivate var imageView = UIImageView()

    private var image: UIImage? {
        get{
            return imageView.image
        }
        set{
            imageView.image = newValue
            imageView.sizeToFit()
            scrollView?.contentSize = imageView.frame.size
        }
    }
}

extension ImageViewController: UIScrollViewDelegate
{
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView
    }
}