Update data in ViewController of UIPageViewController - ios

Question

I have PageViewController and I'm loading ViewController's, every thing working fine. But when i update data in my ViewController of PageViewController it's getting crash in SecondViewController lbl1.text = "New Lbl1".
Error: Fatal error: Unexpectedly found nil while implicitly unwrapping
an Optional value
My Code in PageViewController :
import UIKit
class NewViewController: UIViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
#IBOutlet weak var pagerController: UIPageControl!
#IBOutlet weak var pageControllerView: UIView!
// The pages it contains
var pages = [UIViewController]()
// The UIPageViewController
var pageContainer: UIPageViewController!
// Track the current index
var currentIndex: Int?
private var pendingIndex: Int?
override func viewDidLoad() {
super.viewDidLoad()
// Setup the pages
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let page1 = storyboard.instantiateViewController(withIdentifier: "ViewController") as! ViewController
let page2: UIViewController! = storyboard.instantiateViewController(withIdentifier: "SecondViewController")
let page3: UIViewController! = storyboard.instantiateViewController(withIdentifier: "ThirdViewController")
pages.append(page1)
pages.append(page2)
pages.append(page3)
page1.variable = "This is strig..."
// Create the page container
pageContainer = UIPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
pageContainer.delegate = self
pageContainer.dataSource = self
pageContainer.setViewControllers([page1], direction: UIPageViewController.NavigationDirection.forward, animated: false, completion: nil)
// Add it to the view
pageControllerView.addSubview(pageContainer.view)
// set the frame of the pageContainer view to match its superview (the red view)
pageContainer.view.frame = pageControllerView.bounds
// let it resize if needed (such as device rotation)
pageContainer.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
// Configure our custom pageControl
view.bringSubviewToFront(pagerController)
pagerController.numberOfPages = pages.count
pagerController.currentPage = 0
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - UIPageViewController delegates
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
let currentIndex = pages.firstIndex(of:viewController)!
if currentIndex == 0 {
return nil
}
let previousIndex = abs((currentIndex - 1) % pages.count)
return pages[previousIndex]
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
let currentIndex = pages.firstIndex(of:viewController)!
if currentIndex == pages.count-1 {
return nil
}
let nextIndex = abs((currentIndex + 1) % pages.count)
return pages[nextIndex]
}
func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
pendingIndex = pages.firstIndex(of:pendingViewControllers.first!)
}
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if completed {
currentIndex = pendingIndex
if let index = currentIndex {
pagerController.currentPage = index
}
}
}
#IBAction func barBtnAction(_ sender: UIBarButtonItem) {
SecondViewController().setNewData()
}
}
My code in ViewController :
import UIKit
class SecondViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet weak var tblView: UITableView!
#IBOutlet weak var tblHeight: NSLayoutConstraint!
#IBOutlet weak var lbl1: UILabel!
#IBOutlet weak var lbl2: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
tblView.delegate = self
tblView.dataSource = self
}
#IBAction func btn(_ sender: Any) {
print("ViewController second")
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 5
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell")
cell?.textLabel?.text = "\(indexPath.row)"
return cell!
}
func setNewData() {
lbl1.text = "New Lbl1"
lbl2.text = "New Lbl2"
tblHeight.constant = 250
}
}
My PageVC
My SecondVC

Answer 1

This
SecondViewController().setNewData()
access the 2 nd vc without layout as you should load it from storyboard regradless of outlet connected / not hence a crash , you may need
let sec = pages[1] as! SecondViewController
sec.setNewData()
This SecondViewController() is used when the vc is completely created programmatically when you do it with 1 from storyboard all outlets will be nil as layout isn't loaded with that initializer in addition to that you create a new instance other than the 1 in pager controller