Find CurrentViewcontroller (or TopViewController) in swift

FindCurrentViewcontroller.swift

extension AppDelegate {
    func findCurrentViewController() -> UIViewController{
        let rootVC = UIApplication.sharedApplication().keyWindow?.rootViewController

        return findCurrentViewController(byTempTopVC: rootVC!)
    }
    
    func findCurrentViewController(byTempTopVC vc: UIViewController) -> UIViewController {
        let presentedVC = vc.presentedViewController
    
        guard presentedVC != nil else {
            return vc
        }
        
        if presentedVC!.isKindOfClass(UINavigationController) {
            let theNav =  presentedVC
            let theTopVC = theNav!.childViewControllers.last
            return findCurrentViewController(byTempTopVC: theTopVC!)
        }
        
        return findCurrentViewController(byTempTopVC: presentedVC!)
    }
}