OrdoDei给出了一个正确而有价值的答案。我添加这个答案只是为了给出一个didFinishLaunchingWithOptions方法的例子，该方法使用了他的答案以及其他关于导航控制器的评论。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    // Override point for customization after application launch.

    // Instantiate the main menu view controller (UITableView with menu items).
    // Pass that view controller to the nav controller as the root of the nav stack.
    // This nav stack drives our *entire* app.
    UIViewController *viewController = [[XMMainMenuTableViewController alloc] init];
    self.navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];

    // Instantiate the app's window. Then get the nav controller's view into that window, and onto the screen.
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // [self.window addSubview:self.navigationController.view];
    // The disabled line above was replaced by line below. Fixed Apple's complaint in log: Application windows are expected to have a root view controller at the end of application launch
    [self.window setRootViewController:self.navigationController];
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}

日志中也有同样的错误信息。我在应用中有一个UIAlertView弹出:didFinishLaunchingWithOptions。我通过延迟对alertView的调用来解决这个问题，让根视图控制器有时间完成加载。

在应用程序:didFinishLaunchingWithOptions:

[self performSelector:@selector(callPopUp) withObject:nil afterDelay:1.0];

1秒后调用:

- (void)callPopUp
{
    // call UIAlertView
}

尝试将选项卡栏控制器的IBOutlet连接到接口生成器中的根视图，而不是

self.window.rootViewController = self.tabBarController;

但实际上我还没见过这样的错误。

这发生在我身上。通过编辑.plist文件解决。 指定Main nib文件基名。(应该是MainWindow.xib)。 希望这能有所帮助。

我最近在用ios5 sdk构建一个项目时遇到了同样的问题。 起初，它是构建和运行正常的，但在那之后，错误出现了。 对我来说，解决办法相当简单。 所缺少的是，我的应用程序目标的摘要选项卡中的主界面属性被擦除了。所以我需要重新设置。

如果这不是重点，如果tabBarController仍然是nil，你总是可以通过编程方式创建你的窗口和根控制器。 作为备用方案，我将以下代码添加到我的项目中

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{ 
    if (!window && !navigationController) {
        NSLog(@"Window and navigation controller not loaded from nib. Will be created programatically.");
        self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
        UIViewController *viewController1, *viewController2;
        viewController1 = [[[FirstViewController alloc] initWithNibName:@"FirstViewController_iPhone" bundle:nil] autorelease];
        viewController2 = [[[SecondViewController alloc] initWithNibName:@"SecondViewController_iPhone" bundle:nil] autorelease];

        self.tabBarController = [[[UITabBarController alloc] init] autorelease];
        self.tabBarController.viewControllers = [NSArray arrayWithObjects:viewController1, viewController2, nil];
        self.window.rootViewController = self.tabBarController;

    }
    else {
        [window addSubview:[tabBarController view]];
    }
    [self.window makeKeyAndVisible];
    return YES;
}

只有当sho的解决方案也被实现时，这才会起作用。

我在使用自定义ServiceLocator使用CoreData时得到了这样的错误

let context: NSManagedObjectContext = try self.dependencies.resolve()

//solution
let context: NSManagedObjectContext? = try? self.dependencies.resolve()