Bug when checking back/forward scrolling in UIPageViewCotroller - ios

Question

I am trying to load appropriate images from an array into my UIPageViewController's Views.
I have 3 views which I cycle through in order to prevent crashes.
I keep track whether I am scrolling forward or backwards but sometimes when flipping forth and back really quick, I run into a bug that flips the direction and than I get the same view repeating for couple of scrolls.
Here is the function that updates the local variable index when scrolling completes
func pageViewController(pvc: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if completed {
let thisPage = pvc.viewControllers!.last as! PageContentViewController
let currentIndex = thisPage.pageIndex
let lastIndex = lastPage.pageIndex
if(currentIndex > urlIndex){
urlIndex += 1
}else if(currentIndex < urlIndex) {
urlIndex -= 1
}else{
}
}
}
And here is the rest of my UIPageViewController code:
override func viewDidLoad() {
super.viewDidLoad()
dataSource = self
delegate = self
}
private(set) lazy var orderedViewControllers: [PageContentViewController] = {
return [self.newPageContentViewController(),
self.newPageContentViewController(),
self.newPageContentViewController()
]
}()
private func newPageContentViewController() -> PageContentViewController {
return UIStoryboard(name: "Main", bundle: nil) .
instantiateViewControllerWithIdentifier("PageContentViewController") as! PageContentViewController
}
private func getNextViewController() -> PageContentViewController{
let scrollView = orderedViewControllers.removeAtIndex(0)
orderedViewControllers.append(scrollView)
return scrollView
}
private func getPreviousViewController() -> PageContentViewController{
let scrollView = orderedViewControllers.removeLast()
orderedViewControllers.insert(scrollView, atIndex: 0)
return scrollView
}
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController?
{
guard urlIndex > 0 else {
return nil
}
let previousUrlIndex = urlIndex - 1
return getViewControllerAtIndex(previousUrlIndex, next: false)
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController?
{
let nextUrlIndex = urlIndex + 1
guard arrayRouteName.count > nextUrlIndex else{
return nil
}
return getViewControllerAtIndex(nextUrlIndex, next: true)
}
func getViewControllerAtIndex(index: NSInteger, next: Bool) -> PageContentViewController
{
// Create a new view controller and pass suitable data.
var pageContentViewController:PageContentViewController
if(next){
pageContentViewController = getNextViewController()
}else{
pageContentViewController = getPreviousViewController()
}
pageContentViewController.localImage = arrayLocalImage[index]
pageContentViewController.pageIndex = index
pageContentViewController.view.clipsToBounds = true
return pageContentViewController
}

Answer 1

I have managed to fix the problem. I have removed the pageViewControllerfunction from the UIPageControllerDelegate an simply chaged my pageViewController functions in my data source to get the index from viewController like so
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController?
{
let index = ((viewController as! UIPageContentViewController).pageIndex) - 1
guard index < 0 {
return nil
}
return getViewControllerAtIndex(index, pageContentViewController: getPreviousViewController() )
}
and it behaves like it should.