override func viewDidLoad() {           super.viewDidLoad()     slider.delegate = self     slideControl.currentPageIndicatorTintColor = .clear     slideControl.pageIndicatorTintColor = .clear     slideControl.preferredIndicatorImage = UIImage(named: "pageControlImage")     slideControl.setIndicatorImage(UIImage(named: "activePageImage"), forPage: 0)         }       func scrollViewDidScroll(_ scrollView: UIScrollView) {           let page = slider.contentOffset.x / scrollView.frame.size.width     //slideControl.currentPage = Int(page)     slideControl.setIndicatorImage(UIImage(named: "activePageImage"), forPage: Int(page))         }

override func viewDidLoad() {           super.viewDidLoad() slider.delegate = self     slideControl.currentPageIndicatorTintColor = .clear     slideControl.pageIndicatorTintColor = .clear     slideControl.preferredIndicatorImage = UIImage(named: "pageControlImage")     slideControl.setIndicatorImage(UIImage(named: "activePageImage"), forPage: 0)         }       func scrollViewDidScroll(_ scrollView: UIScrollView) {           let page = slider.contentOffset.x / scrollView.frame.size.width     //slideControl.currentPage = Int(page)     slideControl.setIndicatorImage(UIImage(named: "activePageImage"), forPage: Int(page))         } This is how I have set my page control now. But the images are not appearing.

Primary-Color is one among the custom colours which I have created for my project. And I tried using in-built UIColors, it is just applying background for the whole page control.

Here is the code from the swift file. I call it from the viewDidLoad function. I tried calling it from the viewDidAppear function also but the result is the same. import UIKit extension UIPageControl {   func customPageControl(dotFillColor:UIColor, dotBorderColor:UIColor, dotBorderWidth:CGFloat) {     for (pageIndex, dotView) in self.subviews.enumerated() {       if self.currentPage == pageIndex {         dotView.backgroundColor = dotFillColor         dotView.layer.cornerRadius = dotView.frame.size.height / 2       }else{         dotView.backgroundColor = .white         dotView.layer.cornerRadius = dotView.frame.size.height / 2         dotView.layer.borderColor = dotBorderColor.cgColor         dotView.layer.borderWidth = dotBorderWidth       }     }   } } class IntroSliderViewController: UIViewController, UIScrollViewDelegate {       @IBOutlet weak var slider: UIScrollView!   @IBOutlet weak var slideControl: UIPageControl!       let slide1 = [:]       let slide2 = [:]       let slide3 = [:]       var slides = [ DictionaryString,String ]()       override func viewDidLoad() {     super.viewDidLoad()           slides = [slide1,slide2,slide3]     slider.isPagingEnabled = true     slider.contentSize = CGSize(width: self.view.bounds.width * CGFloat(slides.count), height: self.view.bounds.height)     slider.showsHorizontalScrollIndicator = false     slider.delegate = self     slideControl.customPageControl(dotFillColor: UIColor(named: "Primary-Color")!, dotBorderColor: UIColor(named: "Primary-Color")!, dotBorderWidth: CGFloat(2))           loadSlides()   }       func scrollViewDidScroll(_ scrollView: UIScrollView) {           let page = scrollView.contentOffset.x / scrollView.frame.size.width     slideControl.currentPage = Int(page)         }       func loadSlides() {           for (index,content) in slides.enumerated(){               if let slide = Bundle.main.loadNibNamed("sliderContent", owner: self, options: nil)?.first as? SliderContentView {                   slide.backgroundImage.image = UIImage(named: content["background"]!)         slide.mainImage.image = UIImage(named: content["mainImage"]!)         slide.heading.text = content["heading"]         slide.textContent .text = content["textContent"]                   slider.addSubview(slide)         slide.frame.size.width = self.view.bounds.size.width         slide.frame.size.height = self.view.bounds.size.height         slide.frame.origin.x = CGFloat(index) * self.view.bounds.size.width       }             }         }     }

Thank you for the help. It worked.

The ViewController is displayed using present function. self.present(IntroSliderViewController(), animated: true, completion: nil) And here is the error which occurs when I call this function: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value: file myPlan/IntroSliderViewController.swift, line 25 2021-05-05 16:18:30.705352+0530 myPlan[11130:802505] Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value: file myPlan/IntroSliderViewController.swift, line 25 (lldb)