不导航到特定的视图控制器？

Question

我正在尝试导航到特定的视图控制器，但它无法正常工作。 我正在做的是

    var viewControllers:[UIViewController]!
    var firstView : UIViewController!    

    let storyboard = UIStoryboard(name: "Main", bundle: nil)
        firstView = storyboard.instantiateViewController(withIdentifier: "FirstViewController") as! FirstViewController
        viewControllers = [firstView]

@IBAction func BackAction(_ sender: Any) {
        for aViewController in viewControllers {
            if aViewController is FirstViewController {
                self.navigationController!.popToViewController(aViewController, animated: true)
            }
        }
    }

但没有工作。 我帮我错了。 感谢