所有 IBOutlets 都是零

Question

您好，我正在使用以下代码初始化 viewController：

 var aboutUsViewController = self.storyboard?.instantiateViewControllerWithIdentifier("AboutUsViewController") as AboutUsViewController

在此之后，我转到aboutViewController。但是我在aboutViewController 上的所有IBOutlets 都是nil！为什么呢？ 我正在使用 MMDrawer 库来获得侧边栏菜单。

 var aboutUsViewController = self.storyboard?.instantiateViewControllerWithIdentifier("AboutUsViewController") as AboutUsViewController


        var aboutUsNavController = UINavigationController(rootViewController: aboutUsViewController)

        var appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate

        appDelegate.centerContainer!.centerViewController = aboutUsNavController
        appDelegate.centerContainer!.toggleDrawerSide(MMDrawerSide.Left, animated: true, completion: nil)

在侧边栏上，我选择了关于我们的菜单项，在创建 AboutViewController 并将其移动到左侧之后......问题是当我初始化我的控制器时，出口为零

我在使用 pageViewController 时也遇到了这样的问题：

class ViewController: UIViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {


let pageTitles = ["Title 1", "Title 2", "Title 3", "Title 4"]
var images = ["long3","long4","long1","long2"]
var count = 0


var pageViewController : UIPageViewController!

override func viewDidLoad() {
    super.viewDidLoad()
    reset()
    // Do any additional setup after loading the view, typically from a nib.
}

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

func reset() {
    /* Getting the page View controller */
    pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as UIPageViewController
    self.pageViewController.dataSource = self

    let pageContentViewController = self.viewControllerAtIndex(0)
    self.pageViewController.setViewControllers([pageContentViewController!], direction: UIPageViewControllerNavigationDirection.Forward, animated: true, completion: nil)

    /* We are substracting 30 because we have a start again button whose height is 30*/
    self.pageViewController.view.frame = CGRectMake(0, 0, self.view.frame.width, self.view.frame.height - 30)
    self.addChildViewController(pageViewController)
    self.view.addSubview(pageViewController.view)
    self.pageViewController.didMoveToParentViewController(self)
}



func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {

    var index = (viewController as PageContentViewController).pageIndex!
    index++
    if (index >= self.images.count){
        return nil
    }

    return self.viewControllerAtIndex(index)
}


func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
    var index = (viewController as PageContentViewController).pageIndex!

    if index<=0 {
        return nil
    }
    index--
    return self.viewControllerAtIndex(index)
}

func viewControllerAtIndex(index : Int) -> UIViewController? {
    if((self.pageTitles.count == 0) || (index >= self.pageTitles.count)) {
        return nil
    }
    let pageContentViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageContentViewController") as PageContentViewController

    pageContentViewController.imageName = self.images[index]
    pageContentViewController.titleText = self.pageTitles[index]
    pageContentViewController.pageIndex = index
    return pageContentViewController
}

func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
    return pageTitles.count
}

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

}



class PageContentViewController: UIPageViewController {


@IBOutlet var imageViewMain: UIImageView!

@IBOutlet var labelMain: UILabel!

var pageIndex: Int!
var titleText: String!
var imageName: String!


override func viewDidLoad() {
    super.viewDidLoad()

    self.imageViewMain.image = UIImage(named:imageName)
    self.labelMain.text = self.titleText
    self.labelMain.alpha = 0.1
    UIView.animateWithDuration(1.0, animations:{ ()-> Void in
        self.labelMain.alpha = 1.0
    })
    // Do any additional setup after loading the view.
}

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


/*
// MARK: - Navigation



  // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

我遇到标签和图像出口为零的问题！！！我在使用 MMDrawer 库时遇到了同样的问题。同样的情况。我没有使用 segues ！我想因为那个网点是零

Answer 1

我假设您在实例化场景后立即查看插座（如果使用 segue 并尝试使用 prepareForSegue 中的插座，您也会看到这种行为）。但是，直到您呈现/推送到该场景，加载视图并调用 viewDidLoad 之后，插座才会连接。

底线，在调用viewDidLoad 之前不要尝试使用出口（即不要在实例化场景后立即使用出口）。相反，将所需的数据传递给目标场景（例如 String 属性），然后目标的 viewDidLoad 应该填充出口。

例如，您可能在AboutUsViewController 中有一个属性：

var message: String!

当您实例化 AboutUsViewController 时，您将设置该属性：

let aboutUsViewController = self.storyboard?.instantiateViewControllerWithIdentifier("AboutUsViewController") as AboutUsViewController // use `as!` in Swift 1.2

aboutUsViewController.message = "some message"

presentViewController(aboutUsViewController, animated: true, completion: nil)

然后AboutUsViewController 的viewDidLoad 将使用该属性相应地填充插座：

override func viewDidLoad() {
    super.viewDidLoad()

    label1.text = message
}

但是您永远不会让原始视图控制器尝试设置/调整目标场景的出口。这是AboutUsViewController的责任。

---

只是为了确认一下，您的网点连接正确吗？下面显示了两种确认它们已正确连接的方法。

当您在 Interface Builder 中选择视图控制器然后查看连接检查器时，您是否看到您的插座连接在那里？在以下快照中，label1 已连接，但 label2 未连接：

或者当您查看您的代码并查看插座时，您是否在左边距看到实心点（表示插座已连接）或空点（表示插座未连接）？

Answer 2

您可以在演示前使用此功能，iOS9 及更高版本可用：

    aboutUsViewController.loadViewIfNeeded()

Answer 3

我找到了答案。我没有创建 UIViewController ，而是创建了 UIPageViewController ！！！