Calling delegate function from AppDelegate not working - ios

Question

I am trying to call delegate function in AppDelegate, but seems like it never get invoked.
import UIKit
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate,appdelegate {
var window: UIWindow?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
if let navigationController = window?.rootViewController, let
viewController = navigationController.childViewControllers.first as? ViewController {
viewController.delegate = self
}
// Override point for customization after application launch.
return true
}
func callfromDelegte(indicator: UIActivityIndicatorView) {
indicator.stopAnimating()
}
ViewController-:
import UIKit
protocol appdelegate:class {
func callfromDelegte(indicator:UIActivityIndicatorView)
}
class ViewController: UIViewController {
#IBOutlet weak var indicator: UIActivityIndicatorView!
weak var delegate:appdelegate?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
indicator.startAnimating()
indicator.hidesWhenStopped = true
}
#IBAction func rotateAction(_ sender: UIButton) {
if delegate != nil{
delegate?.callfromDelegte(indicator: indicator)
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
Delegate is always nil, it never goes inside function. What is that i don't
now about delegates yet? How does Google GIDSignInDelegate and its delegate functions get called inside AppDelegate from controller class? I know it might be very stupid question but I would still like to know.Thanks
Ok it worked as i have not embeded my controller with navigationController. So it was not going inside if let. It worked simply like this-:
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// if let navigationController = window?.rootViewController, let
// viewController = navigationController.childViewControllers.first as? ViewController {
// viewController.delegate = self
// }
// Override point for customization after application launch.
let controller = window?.rootViewController as! ViewController
controller.delegate = self
return true
}

Answer 1

You cannot create the Viewcontroller object directly and set the delegate inside your app delegate. You need to access the Viewcontroller object first because it is the inside the rootViewController so you need to implement like this
if let navigationController = window?.rootViewController, let
viewController = navigationController.childViewControllers.first as? ViewController {
viewController.delegate = self
}

Answer 2

You can try to get AppDelegate instance from shared application. Hope it will help
This is Swift 3
#IBAction func rotateAction(_ sender: UIButton) {
let delegate = UIApplication.shared.delegate as? AppDelegate
delegate?.callfromDelegte(indicator: indicator)
}