ios - 可以使用不是 rootViewController 的 NavigationController 来访问和更新 Appdelegate.m 中的 UIWindow 类吗？

Question

调用addMessageFromRemoteNotification应用程序崩溃时：

//Appdelegate.m: these methods assist in showing a speech bubble with a text payload when a message is sent

- (void)application:(UIApplication*)application didReceiveRemoteNotification:(NSDictionary*)userInfo
{
    NSLog(@"Received notification: %@", userInfo);
         [self addMessageFromRemoteNotification:userInfo updateUI:YES];
}

- (void)addMessageFromRemoteNotification:(NSDictionary*)userInfo updateUI:(BOOL)updateUI{

UINavigationController *navigationController = 
    (UINavigationController*)_window.rootViewController;
        ChatViewController *chatViewController = (ChatViewController*).  [navigationController.viewControllers objectAtIndex:0];
            DataModel *dataModel = chatViewController.dataModel;

//
...
}

为了用户体验，初始视图已从NavigationControllerconnected to更改ChatViewController为NavigationControllerconnected to ViewController。

可以ChatViewController和它使用的仍然以编程方式在这些语句中使用，以便在运行时加载视图时调用 addMessageFromRemoteNotification 时NavigationControlelr仍然可以更新？UI

更改 Storyboard 中的初始视图后，rootViewController 类属性显式设置新的初始视图：ViewController 作为方法中的 rootViewController，并且当稍后在屏幕演示中addMessageFromRemoteNotification调用该方法时应用程序崩溃。ChatViewController

调试器窗口

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '- 
[ViewController didSaveMessage:atIndex:]: unrecognized selector sent to instance 0x15d544e0' 

UI当应用程序关闭时在 iPad 上收到通知，但在使用时运行时不更新instantiateViewControllerWithIdentifier。

ChatViewController* chatViewController = (ChatViewController*) 
[ApplicationDelegate.storyBoard instantiateViewControllerWithIdentifier:@"ChatViewController"];
DataModel *dataModel = chatViewController.dataModel;