在第一个ViewController中单击按钮时更改第二个ViewController的标签文本 [英] Changing label text of second ViewController upon clicking button in first ViewController

问题描述

我是Swift和iOS开发的新手。我目前在第一个和标签 ViewControllers ，按钮 $ c>在第二个。我已将第一个按钮连接到第二个 ViewController ，并且转换工作正常。

I'm new to Swift and to iOS Development. I currently have 2 ViewControllers, a button in the first and a label in the second one. I've connected the first button to the second ViewController and the transition works.

现在，当我尝试更改标签的文本时，我收到错误：

Now, when I try changing the label's text I get the error:

致命错误：意外发现为零展开一个可选的
值

fatal error: unexpectedly found nil while unwrapping an Optional value

。

在这里你找到我的第一个 ViewController 中的prepare函数：

Here you find my prepare function in the first ViewController:

 override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "mySegue" {
            let vc = segue.destination as! SecondViewController
            vc.secondResultLabel.text = "Testing"
         }
    }

第二个 ViewController 中的标签是否以某种方式受到保护？

Can it be that the label in the second ViewController is somehow protected ?

感谢您的帮助

推荐答案

您需要将字符串传递给 SecondViewController 而不是指示设置它，因为还没有创建 UILabel 。

You need to pass the String to the SecondViewController instead of directing setting it, as the UILabel has not been created yet.

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "mySegue" {
        let vc = segue.destination as! SecondViewController
        vc.secondResultLabelText = "Testing"
    }
}

并在 SecondViewController viewDidLoad 方法中将 UILabel 设置为是字符串

And in your SecondViewController viewDidLoad method set the UILabel to be the string

var secondResultLabelText : String!

override func viewDidLoad() {

    secondResultLabelText.text = secondResultLabelText
}

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