Extension to UIViewController for easy handling of navigationControllers that are destinationViewControllers

Extension for UIViewController for easy NavCon handling

// as described in CS193P
// If i'm a navigationController, then return my visible View Controller. otherwise, return myself
// now i can send to any viewcontroller, give me the content view controller. if you are the content view controller,
// you give me yourself. if you are a nav controller, you give me the visible view controller

extension UIViewController {
    var contentViewController: UIViewController {
        if let navcon = self as? UINavigationController {
            return navcon.visibleViewController
        }
        else {
            return self
        }
    }
}


// example
override func prepareForSegue() {
    if let ivc = segue.destinationViewController.contentViewController as? ImageViewController {
    
    }

}