swift – 类型UIViewController的值在Xcode 7更新后没有成员topViewController

在我更新到 Xcode 7后,我收到此错误“类型UIViewController的值没有成员topViewController.”其他人遇到这个？ topViewController不再是UIViewController的一部分吗？

override func viewDidLoad() {
    super.viewDidLoad()
    self.navigationItem.leftBarButtonItem = self.editButtonItem()
    let addButton = UIBarButtonItem(barButtonSystemItem: .Search,
        target: self, action: "addButtonPressed:")
    self.navigationItem.rightBarButtonItem = addButton

    if let split = self.splitViewController {
        let controllers = split.viewControllers
        self.detailViewController =
            controllers[controllers.count-1].topViewController as? ### Error heres
        DetailViewController
    }

    model = Model(delegate: self) // create the Model
    model.synchronize() // tell model to sync its data
    self.navigationController?.toolbarHidden = false;
    self.navigationItem.backBarButtonItem = UIBarButtonItem(title:"Home", style:.Plain, target:nil, action:nil)
}

你必须明确它,以便它知道你正在尝试从Swift 2中的UINavigationController获取topViewController：

self.detailViewController = (controllers[controllers.count-1] as! UINavigationController).topViewController