如何在 Swift 中使用标签和选择器视图更改和更新字符串中的某个字符

Question

我有一个 UILabel 当前显示“0000”和一个带有 4 个组件的 pickerView。 每个组件将代表标签中的 4 个字符之一。 因此，组件 1 将更新第一个“0”，第二个组件将更新第二个“0”……依此类推。 我已经成功地使用 obj-c 通过简单地更新字符串来正确更改它们，如下所示：

value = [[NSString alloc] initWithFormat:@"0%@%@%@",

但是当涉及到 Swift 时，我被卡住了。 我可以从字符串中获取字符但不能更新标签。 到目前为止，这是我的代码：

@IBOutlet weak var matchresult: mylabel!

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {


      var value:String = "0000"

      var firstSelection:Int
      var secondSelction:Int
      var thirdSection:Int
      var forthSelection:Int

      firstSelection = pickerView.selectedRow(inComponent:0)
      secondSelction = pickerView.selectedRow(inComponent:1)
      thirdSection = pickerView.selectedRow(inComponent:2)
      forthSelection = pickerView.selectedRow(inComponent:3)


      //First row selected of first component in pickerview
        if  firstSelection == 0 {

       //Get first character in String 'value'
          if var char = value.character(at: 0) {

          print("I found \(char)")

        //Change the 1st character to 0
          char = "0"

          print("I changed after\(char)")

         //update only the first character in string 'value' with 0
         // ???
         mylabel.text = value         
          }


      //Second row selected of first component in pickerview
        } else if  (firstSelection == 1) {

      //Get first character in String 'value'
          if var char = value.character(at: 0) {

          print("I found \(char)")
      //Change the 1st character to 1
          char = "1"

          print("I changed after\(char)")

      //update only the first character in string 'value' with 1
     // ???

   mylabel.text = value

          }

      }

任何帮助都会很棒。

谢谢

Answer 1

简单的解决方案：

而不是字符串声明一个数组，其中包含选择器视图的 4 个选定值

var selectedValues = ["0", "0", "0", "0"]

并假设这是数据源

let numbers = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]

func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 4
}

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return numbers.count
}

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
   return numbers[row]
}

在didSelectRow更新索引处的值，将数组连接到一个字符串并显示它

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    selectedValues[component] = numbers[row]
    matchresult.text = selectedValues.joined()
}