在项目中，我们经常需要获取当前所看到的View Controller，比如从其他App跳回我们的App中时，我们可能需要当前View Controller做些事情。那么怎么获取到当前的View Controller呢？其实非常简单：

extension UIViewController {    class func currentViewController(base: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {        if let nav = base as? UINavigationController {            return currentViewController(base: nav.visibleViewController)        }        if let tab = base as? UITabBarController {            return currentViewController(base: tab.selectedViewController)        }        if let presented = base?.presentedViewController {            return currentViewController(base: presented)        }        return base    }}

给UIViewController加一类方法，静态地获取当前View Controller。这基本上满足了绝大多数情况了。使用时只需：

let theViewControllerYouSee = UIViewController.currentViewController()

点击查看，Enjoy!