Swift-无法将'UINavigationController'类型的值强制转换为'MapViewController'

Question

I'm currently trying to convert my Swift iOS app to Swift 2. I've managed to remove the compiler errors (with some great help from stackoverflow) but I'm running into issues with the app once it's compiled now. My app has a tabBarController with 3 tabs. When I select the 2nd tab, the app now crashes with a 'SIGABRT' error.

I get the error:

Could not cast value of type 'UINavigationController' (0x106fbd588) to 'FlightTracker.MapViewController' (0x105722430)

For the following code:

let mapviewcontroller = self.tabBarController?.viewControllers?[0] as! MapViewController

Why can it not cast the controller as a MapViewController? I had it working this way prior to iOS 9 & Swift 2.

Answer 1

It should work

let navigationController = self.tabBarController?.viewControllers?[0] as! UINavigationController //Check which is your tab on your storyboard, 0, 1, n ?

let mapviewcontroller = navigationController.viewControllers[0] as! MapViewController

self.tabBarController?.viewControllers?[0] => it's your UINavigationController

On your storyboard your tabBarController is connected to N UINavigationController S and one of your UINavigationController to your MapViewController.