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import UIKit
class OnboardingCollectionViewController: UICollectionViewController {
private let pages = OnboardingModelFactory.getPages()
private lazy var pageControl: UIPageControl = {
let pageControl = UIPageControl()
pageControl.numberOfPages = pages.count
return pageControl
override func viewDidLoad() {
private func addPageControlToView() {
pageControl.translatesAutoresizingMaskIntoConstraints = false
pageControl.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -8).isActive = true
pageControl.heightAnchor.constraint(equalToConstant: 40).isActive = true
pageControl.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
extension OnboardingCollectionViewController {
// MARK: UICollectionViewDataSource
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return pages.count
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: OnboardingCollectionViewCell.reuseIdentifier, for: indexPath)
as? OnboardingCollectionViewCell else { fatalError("Could not cast dequeued cell") }
cell.fill(with: pages[indexPath.row])
return cell
extension OnboardingCollectionViewController: UICollectionViewDelegateFlowLayout {
// MARK: UICollectionViewDelegateFlowLayout
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: collectionView.bounds.size.width, height: collectionView.bounds.size.height)
override func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
let pageNumber = Int(targetContentOffset.pointee.x / view.frame.width)
pageControl.currentPage = pageNumber
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