Why is the scroll view being nil?

Question

I have the following code:

extension SegmentedControlViewController: UIScrollViewDelegate {
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        // this checks for whether contentOffset.x is around 10 (contented shifted to the right by 10 points)
        if abs(scrollView.contentOffset.x - 10) < 1 {
            print("works")
        }
    }
}

  @IBOutlet weak var scrollView: UIScrollView!

then I call the function in the viewDidLoad like this:

scrollViewDidScroll(scrollView)

Although I am always getting the error message

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

What am I doing wrong, how to Get the scroll view to not be nil.

Answer 1

Assign the scroll view's .delegate in viewDidLoad() and start scrolling:

class SegmentedControlViewController: UIViewController {

    @IBOutlet weak var scrollView: UIScrollView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // assign the delegate      
        scrollView.delegate = self
        
    }

}

extension SegmentedControlViewController: UIScrollViewDelegate {
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        // this checks for whether contentOffset.x is around 10 (contented shifted to the right by 10 points)
        if abs(scrollView.contentOffset.x - 10) < 1 {
            print("works")
        }
    }
}

---

Edit

If you want to check if the scroll view content has been dragged to the right more than 10 points, use this:

extension SegmentedControlViewController: UIScrollViewDelegate {
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        // this checks for whether contentOffset.x is around 10 (contented shifted to the right by 10 points)
        if scrollView.contentOffset.x < 10 {
            print("scroll content has been dragged to the right more than 10 points")
        }
    }
}