I want to get current index of a pageViewController, I don\'t know how I get the visible pages index.
func pageViewController(pageViewController: UIPageViewContr         
        
Create a method within, for example, class -> WalkthroughPageViewController), such that:
 /* The method takes in a page index and creates the next content view controller. If the controller can
 be created, we call the built-in setViewControllers method and navigate to the next view controller.*/
func forward(index: Int) {
    if let nextViewController = contentViewController(at: index + 1) {
        setViewControllers([nextViewController], direction: .forward, animated: true, completion: nil)
    }
}
And in the class that controls said UIPageController, which will be a controller view (class -> WalkthroughContentViewController) and that contains a following button that passes to the next page and updates the property "pageControl.currentPage" (which is itself the UIpageControl), implements:
class WalkthroughContentViewController: UIViewController {
@IBOutlet var headingLabel: UILabel!
@IBOutlet var contentLabel: UILabel!
@IBOutlet var forwardButton: UIButton!
@IBOutlet var pageControl: UIPageControl!
@IBOutlet var contentImageView: UIImageView!
var index     = 0
var heading   = ""
var content   = ""
var imageFile = ""
override func viewDidLoad() {
    super.viewDidLoad()
    headingLabel.text = heading
    contentLabel.text = content
    contentImageView.image = UIImage(named: imageFile)
    // Update the 'currentPage' property of the page control.
    pageControl.currentPage = index
    if case 0...1 = index {
        forwardButton.setTitle("NEXT", for : .normal)
    } else if case 2 = index {
        forwardButton.setTitle("DONE", for : .normal)
    }
}
// MARK: - Actions
@IBAction func nextButtonTapped(sender: UIButton) {
    switch index {
    case 0...1: /* Get the parent controller & call to the "forward" method from the 'WalkthroughPageViewController'. */
        let pageViewController = parent as! WalkthroughPageViewController
        pageViewController.forward(index: index)
    case 2: /* Dismiss the page view controller and show the main screen of the app*/
        dismiss(animated: true, completion: nil)
    default: break
    }
}
}