Can a navigation controller and its top view controller have a presented view controller at the same time?

Question

I need to find the top most navigation controller of my view controller hierarchy. I couldn't figure for sure if a navigation controller AND it's top view controller can have presented view controllers at the same, i.e

NavigationController --Presented--> UIViewController A

|

|

NavigationController.topViewController --Presented--> UIViewController B

Is this possible simultaneously? As in would i have to traverse both paths to the end and compare which is longer and then choose the correct path?

What I tried

I tried to simultaneously present view controllers on a navigation controller and its top view controller but i get this warning in LLDB "Attempt to present on whose view is not in the window hierarchy!"

It didn't present the view controller (0x100605860) but will this ALWAYS be the case? Can custom presentations leave a view in the window hierarchy?

Answer 1

presentViewController shows a view controller. It doesn't return a view controller. If you're not using a UINavigationController, you're probably looking for presentedViewController and you'll need to start at the root and iterate down through the presented views.

Swift 3.*

extension UIApplication {
class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {
    if let navigationController = controller as? UINavigationController {
        return topViewController(controller: navigationController.visibleViewController)
    }
    if let tabController = controller as? UITabBarController {
        if let selected = tabController.selectedViewController {
            return topViewController(controller: selected)
        }
    }
    if let presented = controller?.presentedViewController {
        return topViewController(controller: presented)
    }
    return controller
}
}

Swift 2

extension UIApplication {
class func topViewController(controller: UIViewController? = UIApplication.sharedApplication().keyWindow?.rootViewController) -> UIViewController? {
    if let navigationController = controller as? UINavigationController {
        return topViewController(navigationController.visibleViewController)
    }
    if let tabController = controller as? UITabBarController {
        if let selected = tabController.selectedViewController {
            return topViewController(selected)
        }
    }
    if let presented = controller?.presentedViewController {
        return topViewController(presented)
    }
    return controller
}
}

You can you use this anywhere on your controller

if let topController = UIApplication.topViewController() {
}