ios - 如何将新数据传递给 UILabel 而不是将数据添加到已经创建的字符串？

Question

每次我点击生成密码都会变大，每次按下按钮时如何更改字符串？

import UIKit

class ViewController: UIViewController {
    
    let lettersAndNumbers = ["a", "b", "c", "d", "e", "1", "2", "3"]
    
    var password: String = ""
    
    @IBOutlet weak var passwordText: UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    @IBAction func generateButton(_ sender: UIButton) {
        for _ in 1...6 {
            password += lettersAndNumbers.randomElement()!
            passwordText.text = password
        }
    }
}

Answer 1

每次generateButton调用时，您只需附加 6 个新字符。

您需要password在添加字符之前重置。

@IBAction func generateButton(_ sender: UIButton) {
    password = ""
    for _ in 1...6 {
        password += lettersAndNumbers.randomElement()!
    }
    passwordText.text = password
}

与您的问题无关，但您不需要在循环的每次迭代中更新文本字段，您只需要在password更新后执行一次。

您也可以完全摆脱循环，使用compactMap然后在一行joined中更新password，因此您不需要重置它，您可以直接分配新值。

@IBAction func generateButton(_ sender: UIButton) {
    password = (1...6).compactMap { _ in lettersAndNumbers.randomElement() }.joined()
    passwordText.text = password
}

Answer 2

将您的generateButton代码替换为这个。

@IBAction func generateButton(_ sender: UIButton) {
        for _ in 1...6 {
            password += lettersAndNumbers.randomElement()!
        }
            passwordText.text = password
    }

Answer 3

您可以didSet在密码更改时更改标签的文本。立即调用 didSet after the new value is saved。

var password: String = "" {
  didSet {
    passwordText.text = password
  }
} 
@IBAction func generateButton(_ sender: UIButton) {
        for _ in 1...6 {
            password += lettersAndNumbers.randomElement()!
        }
    }