Swift 4.2中一个简洁而全面的解决方案，考虑了UINavigationControllers, UITabBarControllers, presenting和子视图控制器:

extension UIViewController {
  func topmostViewController() -> UIViewController {
    if let navigationVC = self as? UINavigationController,
      let topVC = navigationVC.topViewController {
      return topVC.topmostViewController()
    }
    if let tabBarVC = self as? UITabBarController,
      let selectedVC = tabBarVC.selectedViewController {
      return selectedVC.topmostViewController()
    }
    if let presentedVC = presentedViewController {
      return presentedVC.topmostViewController()
    }
    if let childVC = children.last {
      return childVC.topmostViewController()
    }
    return self
  }
}

extension UIApplication {
  func topmostViewController() -> UIViewController? {
    return keyWindow?.rootViewController?.topmostViewController()
  }
}

用法:

let viewController = UIApplication.shared.topmostViewController()

Swift 4.2扩展

extension UIApplication {

    class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {
        if let navigationController = controller as? UINavigationController {
            return topViewController(controller: navigationController.visibleViewController)
        }
        if let tabController = controller as? UITabBarController {
            if let selected = tabController.selectedViewController {
                return topViewController(controller: selected)
            }
        }
        if let presented = controller?.presentedViewController {


            return topViewController(controller: presented)
        }
        return controller
    }
}

在任何地方都可以使用，

 UIApplication.topViewController()?.present(yourController, animated: true, completion: nil)

或者像,

 UIApplication.topViewController()?
                    .navigationController?
                    .popToViewController(yourController,
                                         animated: true)

适合任何类，如UINavigationController, UITabBarController

享受吧!

@implementation UIWindow (Extensions)

- (UIViewController*) topMostController
{
    UIViewController *topController = [self rootViewController];

    while (topController.presentedViewController) {
        topController = topController.presentedViewController;
    }

    return topController;
}

@end

我最近在我的一个项目中遇到了这种情况，当网络状态发生变化时，需要显示一个通知视图，无论显示的控制器是什么，无论类型是什么(UINavigationController，经典控制器或自定义视图控制器)。

所以我刚刚发布了我的代码，这很简单，实际上是基于一个协议，所以它对每种类型的容器控制器都是灵活的。 它似乎与上一个答案有关，但方式更加灵活。

你可以从这里获取代码:PPTopMostController

并得到最顶级的控制器使用

UIViewController *c = [UIViewController topMostController];

斯威夫特5

试试这个

let topVisibleVC = UIApplication.shared.keyWindow?.rootViewController?.visibleViewController

如果根控制器是一个导航控制器，找到顶部可见控制器的正确方法是:

UIViewController *rootVC = [[UIApplication sharedApplication] keyWindow].rootViewController;
if ([rootVC respondsToSelector:@selector(visibleViewController)])
{
    UIViewController *topVC = [(UINavigationController *)rootVC visibleViewController];
    // do your thing with topVC
}

以下是UINavigationController.h的节选:

@property(nonatomic,readonly,retain) UIViewController *topViewController; // The top view controller on the stack.
@property(nonatomic,readonly,retain) UIViewController *visibleViewController; // Return modal view controller if it exists. Otherwise the top view controller.