/**1.创建Storyboard,加载Storyboard的名字,这里是自己创建的Storyboard的名字*/

    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];

UIViewController

 *nav  = [storyboard instantiateViewControllerWithIdentifier:@"nav"];

    

    UIWindow *window = [[[UIApplication sharedApplication]delegate]window];

    window.rootViewController = nav;