How to call a method of another ViewController from Appdelegate? - ios

Question

From my appdelegate I need to execute a method that is from a viewcontroller.
Please, can anybody tell me how to easily have the possibility to call whatever method I need from my appdelegate?
A lot of questions regarding this argument but none of these are useful/complete/right, so please avoid to post URL to other topics: I already checked all questions but I really can't find any precise answer regarding doing this in Swift. :)

Answer 1

It depends on how you've arranged your view controllers but here's an example from a simple iPhone master/detail project.
let root : UINavigationController = self.window!.rootViewController! as UINavigationController
let master : MasterViewController = root.topViewController as MasterViewController
println("\(master.description)")

Answer 2

The way I did it was to search for the view controller I want, starting on AppDelegate's var window: UIWindow? and then going deeper until I find it. I originally tried to implement NSNotification but this is not recommended on swift (I think computed property is a good replace for that, but it don't work in this case).
This is how I did for my tab based application with a NavigationController on top of my ViewController:
if let rootViewController = self.window?.rootViewController as? UITabBarController
if let viewControllers = rootViewController.viewControllers {
for navigationController in viewControllers {
if let yourViewController = navigationController.topViewController as? YourCustomViewController {
if yourViewController.hasSomeFlag {
yourViewController.theMethod()
}
break
}
}
}
}

Answer 3

You can do it with notifications, just add observer to your viewcontroller, post a notification from your app delegate, this observer will catch it and run a function you specify.
this tutorial should help get you started: https://www.codefellows.org/blog/how-to-implement-an-nsnotification-observer-in-swift

Answer 4

Try this
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool {
// Override point for customization after application launch.
return true
}
func customMethod()
{
}
}
Call custom method from ViewController
class ViewController: UIViewController {
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
appDelegate.customMethod()
}