我的If let语句失败，我不确定为什么

问题描述

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")
        }
    }
}

对于第二个标识符为“ JumpSpotInfo”的脚本，我知道代码正在运行if let语句，因为在调试器中显示了print（“ eriubvwribvuorlaeD”），但是我不知道为什么在代码中如果不执行。有什么想法吗？

解决方法

这是一个很好的例子，为什么强制展开会非常有用。

强制解开与segue直接相关的所有可选内容。如果代码崩溃，则您犯了一个设计错误，可以立即修复。如果所有类和标识符都设置正确，则代码不会崩溃。

通过可选绑定，什么也不会发生，而且你也不知道为什么。

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")
    }
}