Swift3 SWRevealViewController零错误

我使用的是SWRevealViewController

当我点击BackButton时，出现了这个错误

fatal error: unexpectedly found nil while unwrapping an Optional value

我的代码

解决方案

解决方案

---

上述方法可以工作，但加载视图控制器后，菜单滑出的SWREVEL功能停止工作！？上述方法可以工作，但加载视图控制器后，菜单滑出的SWREVEL功能停止工作！？

let nesne:SWRevealViewController = self.revealViewController()//the error here
let mainStroyBoard:UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let desController = mainStroyBoard.instantiateViewController(withIdentifier: "MessageViewController") as! MessageViewController
let newFrontViewController = UINavigationController.init(rootViewController:desController)
nesne.pushFrontViewController(newFrontViewController, animated: true)

let sw = storyboard?.instantiateViewController(withIdentifier: "SWRevealViewController") as! SWRevealViewController
self.view.window?.rootViewController = sw

let mainStroyBoard:UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let desController = mainStroyBoard.instantiateViewController(withIdentifier: "MessageViewController") as! MessageViewController
let newFrontViewController = UINavigationController.init(rootViewController:desController)
sw.pushFrontViewController(newFrontViewController, animated: true)