Add a if statement to a notification in Swift - ios

Question

Right now my code presents a alert message immediately when the app loads. I would like to change the code to only display the alert message. If the button is not pressed within 20 seconds of loading. The button action is called pressBUTTON.
import UIKit
class ViewController: UIViewController {
let myNotification = Notification.Name(rawValue:"MyNotification")
override func viewDidLoad() {
super.viewDidLoad()
let nc = NotificationCenter.default
nc.addObserver(forName:myNotification, object:nil, queue:nil, using:catchNotification)
}
#IBAction func pressBUTTON(_ sender: Any) {
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let nc = NotificationCenter.default
nc.post(name:myNotification,
object: nil,
userInfo:["message":"Hello there!", "date":Date()])
}
func catchNotification(notification:Notification) -> Void {
print("Catch notification")
guard let userInfo = notification.userInfo,
let message = userInfo["message"] as? String,
let date = userInfo["date"] as? Date else {
print("No userInfo found in notification")
return
}
let alert = UIAlertController(title: "Notification!",
message:"\(message) received at \(date)",
preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
self.present(alert, animated: true, completion: nil)
}}

Answer 1

Wrap your alert code inside a non-repeating Timer with a 20 seconds delay. In your pressBUTTON function, call invalidate on such timer to disable the notification from showing.
Might be a good idea to invalidate the timer when leaving your view controller as well (e.g., in the viewWillDisapear method).