Can't Call Segue By Identifier from AppDelegate - ios

Question

So I have a segue from ViewController to SecondViewController. This segue is triggered by a UIButton in ViewController and the modally presents SecondViewController. The Segue's Identifier is set ("SegueIdentifier") and I am able to call the segue programatically from within my ViewController.
When I try to do the same in my AppDelegate, I get the error that the compiler can't find a segue with the Identifier I set.
let viewController = ViewController()
viewController.performSegueWithIdentifier("SegueIdentifier", sender: nil)
Again, I literally copied and pasted the performSegueWithIdentifier method call from the aforementioned method in ViewController in which I also call performSegueWithIdentifier for the same segue and it works.
Any ideas?

Answer 1

In my one project I am managing this situation like,
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
NSString *identifier;
BOOL isSaved = [[NSUserDefaults standardUserDefaults] boolForKey:#"loginSaved"];
if (isSaved)
{
identifier=#"home1";
}
else
{
identifier=#"dis1";
}
UIStoryboard * storyboardobj=[UIStoryboard storyboardWithName:#"Main" bundle:nil];
UIViewController *screen = [storyboardobj instantiateViewControllerWithIdentifier:identifier];
[self.window setRootViewController:screen];
return YES;
}
It is in objective c and just for reference. If it can help you :)
Update :
In swift something like,
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
var identifier: String = String()
let isSaved = NSUserDefaults.standardUserDefaults().boolForKey("loginsaved")
if isSaved
{
identifier = "home1"
}
else{
identifier = "dis1"
}
let storyboardobj: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let screen: UIViewController = storyboardobj.instantiateViewControllerWithIdentifier(identifier)
self.window!.rootViewController = screen
// Override point for customization after application launch.
return true
}
Hope this will help :)

Answer 2

If you are not trying to show your initial view then do like this:
UIApplication.sharedApplication().keyWindow?.rootViewController.performSegueWithIdentifier("SegueIdentifier", sender: nil)
And also it depends that you segue is set to your RootViewController. Please check that also before you do this.

Answer 3

Segue connection has some info with it like Source Controller, Destination Controller. So while you are calling the performSegue method from ViewController class, it will work because that class has the info of this Segue connection.
While you are calling that same Segue method from App Delegate, it will not work. Because App Delegate class doesn't have the info or definition about that Segue object.
You should also check whether the calling object comes under Navigation Controller or not.

Answer 4

A storyboard segue has to be tied to the specific viewController that you are trying to segue from. So you have to have an instance of the current view controller on the screen. You may use the UIApplication.sharedApplication().keyWindow?.rootViewController
Method to get access to the rootViewController in the window, however if you presented a view controller above the rootViewController and you want to perform the segue on the presented view controller you have to access the rootViewController.presentedViewController. And since you may have multiple presentedViewControllers, what you do is this:
//get the root view controller
var currentViewController = UIApplication.sharedApplication().keyWindow?.rootViewController
//loop over the presented view controllers and until you get the top view controller
while currentViewController.presentedViewController != nil{
currentViewController = currentViewController.presentedViewController
}
//And finally
currentViewController.performSegueWithIdentifier("identifier", sender: nil)