swift 获取当前view显示的控制器

import Foundation
import UIKit

func currentViewController() -> (UIViewController?) {
   var window = UIApplication.shared.keyWindow
   if window?.windowLevel != UIWindow.Level.normal{
     let windows = UIApplication.shared.windows
     for  windowTemp in windows{
       if windowTemp.windowLevel == UIWindow.Level.normal{
          window = windowTemp
          break
        }
      }
    }
   let vc = window?.rootViewController
   return currentViewController(vc)
}


func currentViewController(_ vc :UIViewController?) -> UIViewController? {
   if vc == nil {
      return nil
   }
   if let presentVC = vc?.presentedViewController {
      return currentViewController(presentVC)
   }
   else if let tabVC = vc as? UITabBarController {
      if let selectVC = tabVC.selectedViewController {
          return currentViewController(selectVC)
       }
       return nil
    }
    else if let naiVC = vc as? UINavigationController {
       return currentViewController(naiVC.visibleViewController)
    }
    else {
       return vc
    }
 }