Opening View Controller from App Delegate Using Swift

Opening view controller from app delegate using swift

You have to set ViewController StoryBoardId property as below image.

open viewController using coding as below in swift

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

         let mainStoryboardIpad : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
         let initialViewControlleripad : UIViewController = mainStoryboardIpad.instantiateViewControllerWithIdentifier("Circles") as UIViewController
         self.window = UIWindow(frame: UIScreen.main.bounds)
         self.window?.rootViewController = initialViewControlleripad
         self.window?.makeKeyAndVisible()

         return true
    }

For iOS 13+ (based on an article by dev2qa)

Open SceneDelegate.swift and add following

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

    // If this scene's self.window is nil then set a new UIWindow object to it.
    self.window = self.window ?? UIWindow()

    // Set this scene's window's background color.
    self.window!.backgroundColor = UIColor.red

    // Create a ViewController object and set it as the scene's window's root view controller.
    self.window!.rootViewController = ViewController()

    // Make this scene's window be visible.
    self.window!.makeKeyAndVisible()

    guard scene is UIWindowScene else { return }
}

There is an open-source navigation utility which attempts to make this easier. Example

set initial viewcontroller in appdelegate - swift

Xcode11 and SceneDelegate note:

Starting from Xcode11, because of SceneDelegates, it's likely that you shouldn't do it inside AppDelegate. Instead do it from SceneDelegate. For more on that see this other answer

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Old answer:

I used this thread to help me convert the objective C to swift, and its working perfectly.

Instantiate and Present a viewController in Swift

Swift 2 code:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
    
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    
    let initialViewController = storyboard.instantiateViewControllerWithIdentifier("LoginSignupVC")
    
    self.window?.rootViewController = initialViewController
    self.window?.makeKeyAndVisible()
    
    return true
}

Swift 3 code:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    self.window = UIWindow(frame: UIScreen.main.bounds)

    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    
    let initialViewController = storyboard.instantiateViewController(withIdentifier: "LoginSignupVC")

    self.window?.rootViewController = initialViewController
    self.window?.makeKeyAndVisible()

    return true
}

How do I open a view controller from the app delegate?

You have 2 possible ways of doing this:

1. Instantiate your tab bar controller via storyboard.

Go to your storyboard and set a storyboard ID for your tab bar controller inside the identity inspector.

Once you go that, you can instantiate your view controller like this:

let storyboard = UIStoryboard(name: storyboardName, bundle: nil)
if let tabController = storyboard.instantiateViewController(withIdentifier: "tabControllerID") as? UITabController {
    tabController.selectedIndex = index
}

2. Or, you can access scene delegate from your AppDelegate and use window -> rootViewController to get access to your tabController:

    let scene = UIApplication.shared.connectedScenes.first
    if let sceneDelegate = scene?.delegate as? SceneDelegate {  
        if let tabController = sceneDelegate.window?.rootViewController as? UITabBarController {
              tabController.selectedIndex = index
        }

    }

Present a view controller from appdelegate

You could use:

[[self window].rootViewController presentViewController:login animated:YES completion:nil];

how to call a method in a view controller from Appdelegate in Swift?

You don’t need to call the view controller method in app delegate. Observe foreground event in your controller and call your method from there itself.

Observe for the UIApplicationWillEnterForeground notification in your viewController viewDidLoad:

NotificationCenter.default.addObserver(self, selector: #selector(ViewController.yourMethod), name: NSNotification.Name.UIApplicationWillEnterForeground, object: nil)

Implement this to receive callback when user enters foreground

@objc func yourMethod() {
     // Call getDateTimeFromServer()
}

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