Почему в Swift произошло «использование необъявленного типа leftViewController»?

Question

Почему я получаю ошибку Use of undeclared type leftViewController, когда я запускаю это в Swift?

var centerContainer: MMDrawerController? 
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool { 
    // Override point for customization after application launch. 
    _ = self.window!.rootViewController 

    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 

    let centerViewController = mainStoryboard.instantiateViewControllerWithIdentifier("ViewController") as! ViewController 

    let leftViewController = self.mainStoryboard?.instantiateViewControllerWithIdentifier("leftViewController") as! leftViewController 

    let rightViewController = mainStoryboard.instantiateViewControllerWithIdentifier("rightViewController") as! rightViewController 

    let leftSideNav = UINavigationController(rootViewController: leftViewController) 
    let centerNav = UINavigationController(rootViewController: centerViewController) 
    let rightNav = UINavigationController(rootViewController: rightViewController) 

    centerContainer = MMDrawerController(centerViewController: centerNav, leftDrawerViewController: leftSideNav,rightDrawerViewController:rightNav) 

    centerContainer!.openDrawerGestureModeMask = MMOpenDrawerGestureMode.PanningCenterView; 
    centerContainer!.closeDrawerGestureModeMask = MMCloseDrawerGestureMode.PanningCenterView; 

    window!.rootViewController = centerContainer 
    window!.makeKeyAndVisible() 


    return true 
} 

Answer 1

Вы должны бросить leftViewController и rightViewController к UIViewController (а не имя экземпляра контроллера представления):

let leftViewController = self.mainStoryboard?.instantiateViewControllerWithIdentifier("leftViewController") as! UIViewController 
let rightViewController = mainStoryboard.instantiateViewControllerWithIdentifier("rightViewController") as! UIViewController