Swift iOS -ScrollView w/ StackView PageController Crash - ios

Question

I followed this programmatic scrollview-pageview tutorial I keep getting a crash inside the Scrollview Delegate's ScrollViewDidScroll(...)
Thread 1: EXC_BREAKPOINT (code=1, subcode=0x1030b0d98)
The crash appears on this line: pageControl.currentPage = Int(round(pageFraction))
Why does this crash keeps happening
ViewController Class:
class ViewController: UIViewController, UIScrollViewDelegate {
let scrollView: UIScrollView = {
let scrollView = UIScrollView()
scrollView.translatesAutoresizingMaskIntoConstraints = false
scrollView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
scrollView.isPagingEnabled = true
scrollView.showsHorizontalScrollIndicator = false
scrollView.backgroundColor = UIColor.white
return scrollView
}()
let stackView: UIStackView = {
let stackView = UIStackView()
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.distribution = .equalSpacing
return stackView
}()
let pageControl: UIPageControl = {
let pageControl = UIPageControl()
pageControl.translatesAutoresizingMaskIntoConstraints = false
pageControl.currentPage = 0
pageControl.tintColor = UIColor.white
pageControl.pageIndicatorTintColor = UIColor.gray
pageControl.currentPageIndicatorTintColor = UIColor.red
pageControl.addTarget(self, action: #selector(pageControlTapped(sender:)), for: .valueChanged)
return pageControl
}()
var views = [UIView]()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.white
scrollView.delegate = self
configureViewsForViewArray()
setScrollViewAnchors()
setStackViewAnchors()
setPageViewsInsideStackView()
setPageControlAnchors()
}
func configureViewsForViewArray(){
let pageView1 = PageView(headerText: "Header 1", paragraphText: "Bla bla bla", backgroundColor: .red)
views.append(pageView1)
let pageView2 = PageView(headerText: "Header 2", paragraphText: "Bla bla bla", backgroundColor: .orange)
views.append(pageView2)
let pageView3 = PageView(headerText: "Header 3", paragraphText: "Bla bla bla", backgroundColor: .blue)
views.append(pageView3)
let pageView4 = PageView(headerText: "Header 4", paragraphText: "Bla bla bla", backgroundColor: .green)
views.append(pageView4)
}
func setScrollViewAnchors(){
view.addSubview(scrollView)
if #available(iOS 11.0, *) {
scrollView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
} else {
scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0).isActive = true
}
if #available(iOS 11.0, *) {
scrollView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
} else {
scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0).isActive = true
}
if #available(iOS 11.0, *) {
scrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 0).isActive = true
} else {
scrollView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
}
if #available(iOS 11.0, *) {
scrollView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: 0).isActive = true
} else {
scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0).isActive = true
}
}
func setStackViewAnchors(){
scrollView.addSubview(stackView)
stackView.leftAnchor.constraint(equalTo: scrollView.leftAnchor).isActive = true
stackView.rightAnchor.constraint(equalTo: scrollView.rightAnchor).isActive = true
stackView.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true
stackView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true
}
func setPageViewsInsideStackView(){
for eachView in self.views{
eachView.translatesAutoresizingMaskIntoConstraints = false
stackView.addArrangedSubview(eachView)
eachView.heightAnchor.constraint(equalTo: view.heightAnchor).isActive = true
eachView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
}
}
func setPageControlAnchors(){
view.addSubview(pageControl)
pageControl.numberOfPages = views.count
if #available(iOS 11.0, *) {
pageControl.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor).isActive = true
} else {
// Fallback on earlier versions
pageControl.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
}
if #available(iOS 11.0, *) {
pageControl.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -20).isActive = true
} else {
// Fallback on earlier versions
pageControl.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -20).isActive = true
}
}
#objc func pageControlTapped(sender: UIPageControl) {
let pageWidth = scrollView.bounds.width
let offset = sender.currentPage * Int(pageWidth)
UIView.animate(withDuration: 0.33, animations: { [weak self] in
self?.scrollView.contentOffset.x = CGFloat(offset)
})
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let pageWidth = scrollView.bounds.width
let pageFraction = scrollView.contentOffset.x/pageWidth
//I get a crash here?
pageControl.currentPage = Int(round(pageFraction))
}
}
// this is the model for the views that get added inside the [UIView] array above
PageView:
import Foundation
import UIKit
class PageView: UIView {
// Private so that it can only be modified from within the class
private var headerTextField = UITextField()
// When this property is set it will update the headerTextField text
var headerText: String = "" {
didSet {
headerTextField.text = headerText
}
}
// Private so that you can only change from within the class
private var paragraphTextView = UITextView()
// When this property is set it will update the paragraphTextView text
var paragraphText: String = "" {
didSet {
paragraphTextView.text = paragraphText
}
}
// Designated Init method
init(headerText: String, paragraphText: String, backgroundColor: UIColor) {
super.init(frame: .zero)
setup()
self.headerTextField.text = headerText
self.paragraphTextView.text = paragraphText
self.backgroundColor = backgroundColor
}
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func setup() {
// Basic text and view setup
headerTextField.isUserInteractionEnabled = false
headerTextField.textColor = .black
headerTextField.textAlignment = .center
headerTextField.sizeToFit()
paragraphTextView.isUserInteractionEnabled = false
paragraphTextView.textColor = .black
paragraphTextView.textAlignment = .center
paragraphTextView.sizeToFit()
paragraphTextView.isScrollEnabled = false
paragraphTextView.backgroundColor = .clear
// Configuring the textfield/view for autoLayout
headerTextField.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(headerTextField)
paragraphTextView.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(paragraphTextView)
// Creating and activating the constraints
NSLayoutConstraint.activate([
headerTextField.centerXAnchor.constraint(equalTo: self.centerXAnchor),
headerTextField.centerYAnchor.constraint(equalTo: self.centerYAnchor),
paragraphTextView.centerXAnchor.constraint(equalTo: self.centerXAnchor),
paragraphTextView.topAnchor.constraint(equalTo: headerTextField.bottomAnchor, constant: 20),
paragraphTextView.widthAnchor.constraint(equalTo: self.widthAnchor, multiplier: (2/3))
])
}
}