Programmatically advance UIPageViewController - Swift - ios

Question

This is my first attempt at an IOS app, and I have no experience with swift, and a lot of the code is borrowed from the web and edited.
I am trying to create a set of slides. I go from the main Landing page to another View Controller, TestVC, that runs the slides. The landing page and the slides work. I can swipe back and forth. I am now trying to add a timer so that the slides auto advance every 5 or so seconds.
I believe that the code that needs to be run is:
pageViewController.setViewControllers(varPageVC, direction: UIPageViewControllerNavigationDirection.forward, animated: true, completion: nil)
I get an error :
test.swift:31:9: Ambiguous reference to member 'pageViewController(_:viewControllerBefore:)'.
I do not know how to interpret this error and move forward. The error is triggered in the test.swift, where a timer calls a function that tries to advance the slide. Advise is appreciated. If I am doing it wrong, please point me in the appropriate direction.
The landing page has a button, that opens a ViewController testVC. I have 2 files, test.swift and alphabetItemController.swift. The storyboard has, in addition to the landing page ViewController, a PageViewController called alphabetPVC, a ViewController called alphabetVC and a ViewController called TestVC.
Here is the code for alphabetItemController.swift ...
import UIKit
class alphabetItemController: UIViewController {
#IBOutlet weak var contentImageView2: UIImageView!
#IBOutlet weak var contentWordPn: UILabel!
var itemIndex: Int = 0
var imageName: String = ""
var wordPN: String = ""
var tTime: Timer!
override func viewDidLoad() {
super.viewDidLoad()
contentImageView2!.image = UIImage(named: imageName)
contentWordPn!.text = wordPN
}
}
Here is the code for test.swift ...
import Foundation
import UIKit
class testItemController: UIViewController, UIPageViewControllerDataSource {
var tTime: Timer!
override func viewDidLoad() {
super.viewDidLoad()
createPageViewController()
setupPageControl()
tTime = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(changeSlide), userInfo: nil, repeats: true)
//tTime = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(goToNextPage), userInfo: nil, repeats: true)
}
func changeSlide() {
pageViewController.setViewControllers(varPageVC, direction: UIPageViewControllerNavigationDirection.forward, animated: true, completion: nil)
}
// MARK: - Variables
private var varPageVC: UIPageViewController?
private let contentTextWordPN = ["A", "B", "C", "D", "E"]
private let contentCount = 5 //TODO ADJUST THIS FOR EACH COLLECTION
private func createPageViewController() {
let pageController = self.storyboard!.instantiateViewController(withIdentifier: "alphabetPVC") as! UIPageViewController
pageController.dataSource = self
if contentCount > 0 {
let firstController = getItemController(itemIndex: 0)!
let startingViewControllers = [firstController]
pageController.setViewControllers(startingViewControllers, direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil)
}
varPageVC = pageController
addChildViewController(varPageVC!)
self.view.addSubview(varPageVC!.view)
varPageVC!.didMove(toParentViewController: self)
}
private func setupPageControl() {
let appearance = UIPageControl.appearance()
appearance.pageIndicatorTintColor = UIColor.gray
appearance.currentPageIndicatorTintColor = UIColor.white
appearance.backgroundColor = UIColor.darkGray
}
func pageViewController(_ varPageVC: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
let itemController = viewController as! alphabetItemController
if itemController.itemIndex > 0 {
return getItemController(itemIndex: itemController.itemIndex-1)
}
return nil
}
func pageViewController(_ varPageVC: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
let itemController = viewController as! alphabetItemController
if itemController.itemIndex+1 < contentCount {
return getItemController(itemIndex: itemController.itemIndex+1)
}
return nil
}
private func getItemController(itemIndex: Int) -> alphabetItemController? {
if itemIndex < contentCount {
let pageItemController = self.storyboard!.instantiateViewController(withIdentifier: "alphabetVC") as! alphabetItemController
pageItemController.itemIndex = itemIndex
pageItemController.imageName = "alphabet_" + String(format: "%02d", (itemIndex + 1)) //alphabet_01
pageItemController.wordPN = contentTextWordPN[itemIndex]
return pageItemController
}
return nil
}
func presentationCountForPageViewController(varPageVC: UIPageViewController) -> Int {
return contentCount
}
func presentationIndexForPageViewController(varPageVC: UIPageViewController) -> Int {
return 0
}
func currentControllerIndex() -> Int {
let pageItemController = self.currentController()
if let controller = pageItemController as? alphabetItemController {
return controller.itemIndex
}
return -1
}
func currentController() -> UIViewController? {
if (self.varPageVC?.viewControllers?.count)! > 0 {
return self.varPageVC?.viewControllers![0]
}
return nil
}
}
extension UIPageViewController {
func goToNextPage(animated: Bool = true) {
guard let currentViewController = self.viewControllers?.first else { return }
guard let nextViewController = dataSource?.pageViewController(self, viewControllerAfter: currentViewController) else { return }
setViewControllers([nextViewController], direction: .forward, animated: animated, completion: nil)
}
func goToPreviousPage(animated: Bool = true) {
guard let currentViewController = self.viewControllers?.first else { return }
guard let previousViewController = dataSource?.pageViewController(self, viewControllerBefore: currentViewController) else { return }
setViewControllers([previousViewController], direction: .reverse, animated: animated, completion: nil)
}
}
There is even an extension UIPageViewController, but I do not know how to call the goToNextPage function.

Answer 1

I ended up changing the changeSlide() function... I had the next slide function in the extension already, and only the syntax to call it was eluding me... I found some examples on SO and used them as references:
func changeSlide() {
varPageVC?.goToNextPage()
}