//MARK: - 查找顶层控制器、
/// 获取顶层控制器 根据window
func getTopVC() -> (UIViewController?) {
    var window = UIApplication.shared.keyWindow
    //是否为当前显示的window
    if window?.windowLevel != UIWindowLevelNormal{
        let windows = UIApplication.shared.windows
        for  windowTemp in windows{
            if windowTemp.windowLevel == UIWindowLevelNormal{
                window = windowTemp
                break
            }
        }
    }

    let vc = window?.rootViewController
    return getTopVC(withCurrentVC: vc)
}

///根据控制器获取 顶层控制器
func getTopVC(withCurrentVC VC :UIViewController?) -> UIViewController? {

    if VC == nil {
        print("🌶： 找不到顶层控制器")
        return nil
    }

    if let presentVC = VC?.presentedViewController {
        //modal出来的 控制器
        return getTopVC(withCurrentVC: presentVC)
    }
    else if let tabVC = VC as? UITabBarController {
        // tabBar 的跟控制器
        if let selectVC = tabVC.selectedViewController {
            return getTopVC(withCurrentVC: selectVC)
        }
        return nil
    } else if let naiVC = VC as? UINavigationController {
        // 控制器是 nav
        return getTopVC(withCurrentVC:naiVC.visibleViewController)
    }
    else {
        // 返回顶控制器
        return VC
    }
}

摘自：https://www.jianshu.com/p/8dd7b57f387f