对于Swift 5+， iOS 13 +

extension UIViewController {
    static func topMostViewController() -> UIViewController? {
        if #available(iOS 13.0, *) {
            let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
            return keyWindow?.rootViewController?.topMostViewController()
        }
        
        return UIApplication.shared.keyWindow?.rootViewController?.topMostViewController()
    }
    
    func topMostViewController() -> UIViewController? {
        if let navigationController = self as? UINavigationController {
            return navigationController.topViewController?.topMostViewController()
        }
        else if let tabBarController = self as? UITabBarController {
            if let selectedViewController = tabBarController.selectedViewController {
                return selectedViewController.topMostViewController()
            }
            return tabBarController.topMostViewController()
        }
            
        else if let presentedViewController = self.presentedViewController {
            return presentedViewController.topMostViewController()
        }
        
        else {
            return self
        }
    }
}

用法:

当你在没有UIViewController实例的情况下获取topMostViewController时

guard let viewController = UIViewController.topMostViewController() else { return }
print(viewController)

当你获取UIViewController实例的topMostViewController时

let yourVC = UIViewController()
guard let vc = yourVC.topMostViewController() else { return }
print(vc)

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
    }

你可以在AppDelegate中定义一个UIViewController变量，并在每个viewWillAppear中设置这个变量为self。(然而，dianz的答案是最好的答案。)

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    let appDel = UIApplication.sharedApplication().delegate as! AppDelegate
    appDel.currentVC = self
}

斯威夫特 5+

声明

func topViewController() -> UIViewController? {
    
    let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first

    if var topController = keyWindow?.rootViewController {
        
        while let presentedViewController = topController.presentedViewController {
            topController = presentedViewController
        }
        
        return topController
        
    } else {
        
        return nil
        
    }
    
}

Use

topViewController()?.view.addSubview(UIView())

有这个扩展

斯威夫特2。*

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

斯威夫特3

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
    }
}

然后你可以在控制器的任何地方使用它

if let topController = UIApplication.topViewController() {
    
}

使用这段代码找到top most UIViewController

func getTopViewController() -> UIViewController? {
    var topController: UIViewController? = UIApplication.shared.keyWindow?.rootViewController
    while topController?.presentedViewController != nil {
        topController = topController?.presentedViewController
    }
    return topController
}