Swift3 无法将类型的值强制转换为'；UIPageViewController'；

所以我对iOS开发还不熟悉。我试图制作一个页面滑动功能，比如一个图像旋转木马或者一个应用程序教程，我遇到了一个线程1:signal SIGABRT错误。日志中的状态为“无法将“ViewController”类型的值强制转换为“UIPageViewController”

不确定您是否需要完整的代码

我的问题是：

self.pageViewController = self.storyboard?.instantiateViewController(withIdentifier: "contentViewController") as! UIPageViewController

非常感谢您的帮助

class ViewController: UIViewController, UIPageViewControllerDataSource {

var pageViewController: UIPageViewController!
var pageTitles: NSArray!
var pageImages: NSArray!



override func viewDidLoad() {


    self.pageTitles = NSArray(objects: " By Request","Subscription Plan","Flex Plan","Everyday Plan", "Welocme")
    self.pageImages = NSArray(objects: "page1","page2","page3","page4","page5")

    self.pageViewController = self.storyboard?.instantiateViewController(withIdentifier: "contentViewController") as! UIPageViewController
    self.pageViewController.dataSource = self

    let startVC = self.viewControllerAtIndex(index: 0) as ContentViewController

    let viewControllers = NSArray(object: startVC)

    self.pageViewController.setViewControllers(viewControllers as? [UIViewController], direction: .forward, animated: true, completion: nil)

    self.pageViewController.view.frame = CGRect(x: 0, y:0, width: Int(self.view.frame.width), height: Int(self.view.frame.size.height - 60))

    self.addChildViewController(self.pageViewController)
    self.view.addSubview(self.pageViewController.view)
    self.pageViewController.didMove(toParentViewController: self)
    super.viewDidLoad()

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}



@IBAction func loginAction(_ sender: AnyObject) {


}


@IBAction func signupAction(_ sender: AnyObject) {


}

func viewControllerAtIndex(index: Int) -> ContentViewController {

    if ((self.pageTitles.count == 0) || (index >= self.pageTitles.count)) {

        return ContentViewController()
    }

    var vc: ContentViewController = self.storyboard?.instantiateViewController(withIdentifier: "pageViewController") as! ContentViewController

    vc.imageFile = self.pageImages[index] as! String
    vc.titleText = self.pageTitles[index] as! String
    vc.pageIndex = index


    return vc

}
// MARK: - Page Vuew Controller Data Source

func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
    let vc = viewController as! ContentViewController
    var index = vc.pageIndex as Int

    if ((index == 0) || (index == NSNotFound)) {
        return nil
    }
    index -= 1

    return self.viewControllerAtIndex(index: index)

}

func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
    var vc = viewController as! ContentViewController
    var index = vc.pageIndex as Int

    if (index == NSNotFound) {
        return nil
    }

    index += 1

    if (index == self.pageTitles.count) {

        return nil

    }

    return self.viewControllerAtIndex(index: index)

}

func presentationCount(for pageViewController: UIPageViewController) -> Int {
    return self.pageTitles.count
}

func presentationIndex(for pageViewController: UIPageViewController) -> Int {
    return 0
}

---

}

在哪里发生的？哪一行？self.pageViewController=self.storyboard？.instanceeviewcontroller（标识符为：“contentViewController”）为！UIPageViewControllerline 25在我的电脑上看起来ID为“contentViewController”的视图控制器不是UIPageViewController。尝试在故事板中更改它。现在，我遇到了相同的问题，但代码行出现了相反的问题：var vc:ContentViewController=self.storyboard？.instanceeviewcontroller（带有标识符：“pageViewController”）as！ContentViewControllerWhere发生这种情况？哪一行？self.pageViewController=self.storyboard？.instanceeviewcontroller（标识符为：“contentViewController”）为！UIPageViewControllerline 25在我的电脑上看起来ID为“contentViewController”的视图控制器不是UIPageViewController。尝试在故事板中更改它。现在，我遇到了相同的问题，但代码行出现了相反的问题：var vc:ContentViewController=self.storyboard？.instanceeviewcontroller（带有标识符：“pageViewController”）as！ContentViewController