Question

我在didSelectRow功能

中的选择器视图中遇到了我的应用程序问题

在某些情况下，选择器视图可能为零，因此didSelectRow内的所有指令都会读取无值，并且应用程序崩溃。

我多次使用不同的解决方案来防止此次崩溃，但它无法正常工作：

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)  {
        if (self.MEDARRAY[row].value(forKey: "medNumDay") as? NSInteger) != nil {

        let NumDay = self.MEDARRAY[row].value(forKey: "medNumDay") as? NSInteger
        let NumMed = self.MEDARRAY[row].value(forKey: "medNum") as? NSInteger
        Counter = (self.MEDARRAY[row].value(forKey: "takenCounter") as? NSInteger)!
        theTimeSet = (self.MEDARRAY[row].value(forKey: "nextTime")as? Date)!
        numberforday = (24 / NumDay!)
        thegetting.timeStyle = DateFormatter.Style.short
        TotalDose.text = String(NumDay! * NumMed!)
        RemainDose.text = String(Int(TotalDose.text!)! - Counter!)
        NextTimes.text = thegetting.string(from: theTimeSet!)
        }
        else{
                TotalDose.text = "No"
                RemainDose.text = "No"
                NextTimes.text = "No"            
        }
}

另一次尝试

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)  {
        if (MEDARRAY.count < 1) {
    let NumDay = self.MEDARRAY[row].value(forKey: "medNumDay") as? NSInteger
    let NumMed = self.MEDARRAY[row].value(forKey: "medNum") as? NSInteger
    Counter = (self.MEDARRAY[row].value(forKey: "takenCounter") as? NSInteger)!
    theTimeSet = (self.MEDARRAY[row].value(forKey: "nextTime")as? Date)!
    numberforday = (24 / NumDay!)
    thegetting.timeStyle = DateFormatter.Style.short
    TotalDose.text = String(NumDay! * NumMed!)
    RemainDose.text = String(Int(TotalDose.text!)! - Counter!)
    NextTimes.text = thegetting.string(from: theTimeSet!)
    }
    else{
            TotalDose.text = "No"
            RemainDose.text = "No"
            NextTimes.text = "No"            
    }
}

问题是它仍然试图通过此错误获取以下代码的值：索引超出范围

let NumDay = self.MEDARRAY[row].value(forKey: "medNumDay") as? NSInteger
let NumMed = self.MEDARRAY[row].value(forKey: "medNum") as? NSInteger
Counter = (self.MEDARRAY[row].value(forKey: "takenCounter") as? NSInteger)!
theTimeSet = (self.MEDARRAY[row].value(forKey: "nextTime")as? Date)!

Answer 1

如果您要识别的项目是选项，但您需要它们具有非零值来执行该函数，请在函数的头部放置一个保护语句，用于测试每个值是否可用：

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    guard row < MEDARRAY.count,
          MEDARRAY.count < 1,
          let NumDay : NSInteger = self.MEDARRAY[row].value(forKey: "medNumDay") as NSInteger,
          let NumMed = self.MEDARRAY[row].value(forKey: "medNum") as NSInteger,
          let Counter = (self.MEDARRAY[row].value(forKey: "takenCounter") as NSInteger
          let theTimeSet = (self.MEDARRAY[row].value(forKey: "nextTime") as Date else { print("Could not obtain all required values") ; return }

     // ... function continues here...

请注意，您可以使用逗号链接guard语句，并且这些常量不是选项：如果非nil值可用，则它们将初始化为非可选，否则将触发保护异常。（另请注意对阵列测试和行输入的更正。）

这样，如果您无法将这些常量初始化为非零值，则该函数将退出，这将阻止应用程序崩溃。当然，这并没有解决为什么值为零，但至少会继续执行。

希望有所帮助。

Swift中的Picker视图

1 个答案: