swift ios - How to run function in ViewController from AppDelegate

Question

I am trying to run a function in certain ViewController using AppDelegate

func applicationDidBecomeActive(_ application: UIApplicat         


        

Answer 1

ViewController().grabData() will create a new instance of the ViewController and call this function. Then.. as the view controller is not in use it will be garbage collected/removed from memory. You need to be calling this method on the actual view controller that is in use. Not a new instance of it.

The best option would be to listen for the UIApplicationDidBecomeActive notification that iOS provides.

NotificationCenter.default.addObserver(
    self,
    selector: #selector(grabData),
    name: NSNotification.Name.UIApplicationDidBecomeActive,
    object: nil)

make sure that you also remove the observer, this is usually done in a deinit method

deinit() {
    NotificationCenter.default.removeObserver(self)
} 

Answer 2

I simply solved it like this:

func applicationDidBecomeActive(_ application: UIApplication) {
        let viewController = self.window?.rootViewController as! ViewController
        viewController.grabData()
}