Aassigning a value to a view controller from AppDelegate.swift

Question

I try to assign a value to a view controller from AppDelegate.swift without success.

My controller is named DestinationsViewController , and its id in Main.storyboard is destinationsID . DestinationsController is embed in a Navigation Controller. The objet I want to change is named "label". This is the code:

if let destinationsViewController = storyBoard.instantiateViewControllerWithIdentifier("destinationsID") as? DestinationsViewController {
       if let label = destinationsViewController.label{
            label.text = "Super!"
        }
        else{
            println("Not good 2")
        }
    }
    else {
        println("Not good 1")
    }

Unfortunately, I get the message: "Not good 2". This is not good :-(

Thank you.

import UIKit

class DestinationsViewController: UIViewController {

@IBOutlet weak var label: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
    }
}

Answer 1

Ok, here's how you can do it. However, if you change the structure of your storyboard then this may break.

First, in DestinationsViewController, you need to set a variable that will hold the text because we're setting the text before the view is rendered. Therefore, the label will not exist yet. When the view loads, it'll set the label.

class DestinationsViewController: UIViewController {

@IBOutlet weak var label: UILabel!
var labelText = String()

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.
    label.text = labelText
}

Now, in the AppDelegate, we set the variable that will set the label when the view loads.

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Override point for customization after application launch.

    // assuming inital view is tabbar
    let tabBarController = self.window?.rootViewController as UITabBarController
    let tabBarRootViewControllers: Array = tabBarController.viewControllers!

    // assuming first tab bar view is the NavigationController with the DestinationsViewController
    let navView = tabBarRootViewControllers[0] as UINavigationController 
    let destinationsViewController = navView.viewControllers[0] as DestinationsViewController
    destinationsViewController.labelText = "Super!"

    return true
}

EDIT

After re-reading your last comment, I realized you want to set the label at some point after the app has already been running. You can just move the code in func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool to where you need it. Then you can also set the label directly, because the view has been loaded.

// assuming inital view is tabbar
let tabBarController = self.window?.rootViewController as UITabBarController
let tabBarRootViewControllers: Array = tabBarController.viewControllers!

// assuming first tab bar view is the NavigationController with the DestinationsViewController
let navView = tabBarRootViewControllers[0] as UINavigationController 
let destinationsViewController = navView.viewControllers[0] as DestinationsViewController

if let label = destinationsViewController.label{
    label.text = "Super DUper!"
}
else{
    println("Not good 2")
}