摘自http://blog.sunnyxx.com/2015/12/19/self-manager-pattern-in-ios/
iOS 開發(fā)中的 Self-Manager 模式
// 假設(shè) App 結(jié)構(gòu)是 Root -> TabBar -> Navigation -> ViewController
UITabBarController *tabBarControler = (id)UIApplication.sharedApplication.delegate.window.rootViewController;
UINavigationController *navigationController = tabBarControler.selectedViewController;