无敌获取控制器

swif：

let tabBarController: UITabBarController = UIApplication.sharedApplication().keyWindow?.rootViewController as! UITabBarController

let nav: UINavigationController = tabBarController.selectedViewController as! UINavigationController

接下来就可以push出去

nav.pushViewController(vc, animated: true)

在你箱套太多层view情况下，或者xib情况下无法获取时，就可以使用，万能的

还可以这样子哦，获取你想要的tab

let tabBarController = UIApplication.sharedApplication().keyWindow?.rootViewController

let nav = tabBarController?.childViewControllers

let home:UINavigationController = nav![0] as! UINavigationController

OC：

UITabBarController *tabBarController = (UITabBarController *)self.window.rootViewController;

UINavigationController * nav = tabBarController.selectedViewController;

UIViewController *viewController = nav.viewControllers[0];