Error while removing story board in 'swift' project. Error : "fatal error: unexpectedly found nil while unwrapping an Optional value"

Question

我一直在学习 Swift 语言，因为我对 Objective-C 有一定的了解。我需要从我的 Swift 项目中删除故事板。我删除了故事板文件，删除了相应的 plist 键，添加了带有 XIB 的新视图控制器，并在应用程序委托中添加了以下代码：

var window: UIWindow?

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        // Override point for customization after application launch.

        window = UIWindow(frame: UIScreen.mainScreen().bounds)
        if let window = window {
            window.backgroundColor = UIColor.whiteColor()
            window.rootViewController = FirstViewController()
            window.makeKeyAndVisible()
        }

        return true
    }

我向 FirstViewController 的 XIB 添加了单个标签，还添加了适当的自动布局约束。

问题是，尽管正在调用 FirstViewController 的 viewDidLoad，但我看不到标签。后来，我将 IBOutlet 添加到标签中，并通过以下代码以编程方式在 viewDidLoad 中设置其文本：

lblHello!.text = "Hello !!!"

在这个阶段，我收到错误：

"fatal error: unexpectedly found nil while unwrapping an Optional value"

我已经交叉检查了 File's owner 和其他 IBOutlet 中的所有内容。我没有发现任何遗漏。

如果我的愚蠢错误遗漏了什么，请告诉我。对于这种情况，我还需要做些什么吗？

Answer 1

这是我的代码片段，它正在运行

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Override point for customization after application launch.

    self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
    self.window!.backgroundColor = UIColor.whiteColor()
    self.window!.rootViewController = ViewController()
    self.window!.makeKeyAndVisible()
    return true
}

和viewDidLoad()共FirstViewController.swift

class ViewController: UIViewController {

@IBOutlet var lblTitle:UILabel?

//MARK: - View lifecycle

override func viewDidLoad() {

    super.viewDidLoad()
    self.lblTitle!.text = "Hello....!!!"
}

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

Error while removing story board in 'swift' project. Error : "fatal error: unexpectedly found nil while unwrapping an Optional value"

Error while removing story board in 'swift' project. Error : "fatal error: unexpectedly found nil while unwrapping an Optional value"

objective-c

storyboard

uiviewcontroller

ios

swift