我的 If let 语句失败了，我不确定为什么

Question

这是我的代码：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    
    // Make sure we are acting on the correct segue
    if segue.identifier == "CreateJumpSpot", let jumpSpotCreatorControllerVC = segue.destination as? JumpSpotCreatorController {
        // Set the delegate in the JumpSpotCreatorController we're navigating to
        jumpSpotCreatorControllerVC.delegate = self
        
    } else if segue.identifier == "JumpSpotInfo", let jumpSpotInfoVC = segue.destination as? JumpSpotInfoController {
        print("eriubvwribvuorlaeD")
        if let senderAnnotationView = sender as? JumpSpotAnnotationView {
            let senderAnnotation = senderAnnotationView.annotation as? JumpSpotAnnotation
            jumpSpotInfoVC.titleLabel.text = senderAnnotation?.title
            jumpSpotInfoVC.imageView.image = senderAnnotation?.image
            jumpSpotInfoVC.descriptionLabel.text = senderAnnotation?.description
            jumpSpotInfoVC.heightLabel.text = senderAnnotation?.estimatedHeight
            jumpSpotInfoVC.warningsLabel.text = senderAnnotation?.warnings
            print("YOYOYOYO")
        }
    }
}

对于第二个 segue，标识符为“JumpSpotInfo”，我知道代码正在执行 if let 语句，因为调试器中出现了 print(“eriubvwribvuorlaeD”)，但我不知道为什么代码在 if let 内部不会执行。有什么想法吗？

Answer 1

这是强制展开非常有用的一个很好的例子。

强制解包所有与 segue 直接相关的选项。如果代码崩溃，您犯了 design 错误，可以立即修复。如果所有类和标识符设置正确，代码不得崩溃。

使用可选绑定什么也不会发生，你也不知道为什么。

并且您不能直接将值分配给标签。您需要在目标视图控制器中声明属性并在 viewDidLoad

中分配值

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    
    // Make sure we are acting on the correct segue
    if segue.identifier == "CreateJumpSpot" {
       let jumpSpotCreatorControllerVC = segue.destination as! JumpSpotCreatorController
        // Set the delegate in the JumpSpotCreatorController we're navigating to
        jumpSpotCreatorControllerVC.delegate = self
        
    } else if segue.identifier == "JumpSpotInfo" {
        let jumpSpotInfoVC = segue.destination as! JumpSpotInfoController          
        print("eriubvwribvuorlaeD")
        let senderAnnotationView = sender as! JumpSpotAnnotationView
        let senderAnnotation = senderAnnotationView.annotation as! JumpSpotAnnotation
        // create the following properties in JumpSpotInfoController
        jumpSpotInfoVC.title = senderAnnotation.title
        jumpSpotInfoVC.image = senderAnnotation.image
        jumpSpotInfoVC.description = senderAnnotation.description
        jumpSpotInfoVC.height = senderAnnotation.estimatedHeight
        jumpSpotInfoVC.warnings = senderAnnotation.warnings
        print("YOYOYOYO")
    }
}

我的 If let 语句失败了，我不确定为什么

My If let statement is failing and I'm not sure why

ios

swift

xcode

if-statement

mapkit