PagedMediaViewControllerDataSource.swift

extension PagedMediaViewController: UIPageViewControllerDataSource {

	pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
		guard currentIndex > 0 else { return nil }
		return mediaViewControllerAtIndex(currentIndex - 1)
	}


	pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
		guard currentIndex < mediaItems.count - 1 else { return nil }
		return mediaViewControllerAtIndex(currentIndex + 1)
	}
}