Swift:Updating UILabel from AppDelegate label doesn't update - ios

Question

I'm trying to update UILabel from appDelegate but the label never change the text. Here is my code:
ViewController:
#IBOutlet weak var lblToUpdate: UILabel?
Here is my app delegate:
DispatchQueue.main.async{
let storyboard = UIStoryboard(name:"Main", bundle:nil)
let myVC = storyboard.instantiateViewController(withIdentifier: "myVC") as! myViewController
if let text = newText{
myVC.text?.text = text
}
}
I have no errors of any kind but the the label never updates.
Any of you knows why the label never gets updated?
I'll really appreciate your help.

Answer 1

The problem is that this VC
let myVC = storyboard.instantiateViewController(withIdentifier: "myVC") as! myViewController
is not the presented one you have to query the window for it and change it's label as you currently play with another one

Answer 2

its not working because the label doesn't exists in the time, just pass the value to a variable in your next controller and then in some of the methods for example :
viewdidload you can update your label with the value of the variable for example :
DispatchQueue.main.async{
let storyboard = UIStoryboard(name:"Main", bundle:nil)
let myVC = storyboard.instantiateViewController(withIdentifier: "myVC") as! myViewController
if let text = newText{
myVC.theVariable = text
}
}
class NextViewController: UIViewController {
var theVariable = ""
override func viewDidLoad() {
super.viewDidLoad()
lblToUpdate.text = theVariable
}

Answer 3

You shouldn't create new instance because is other viewcontroller, this already exist.
You should access to rootViewcontroller and follow window hierarchy
DispatchQueue.main.async{
if let vcroot = self.window!.rootViewController {
if let text = newText{
vcroot.text?.text = text
}
}
}
This code above is example to refer you question.
If you have navigationcontroller is for example:
DispatchQueue.main.async{
if let navroot = self.window!.rootViewController as? NavigationController{
if let childvc = navroot.childviewcontrollers.first {
if let text = newText{
childvc.text?.text = text
}
}
}
}
If have severals viewcontroller in navigation controller you will access using for loop and check and arrive to the viewcontroller that wish change value property or set values