如何解决问题 UIPickerView 致命错误：索引超出范围 [IOS Swift 5.1 Xcode 11.2]

Question

我正在尝试获取UIPickerView 的选定值 运行应用程序时。但我得到错误，

致命错误：索引超出范围

我通过print("selected ==>\(selected)") 在numberOfRowsInComponent 函数中进行调试。我通过调试为 0 得到 selected 的值。

如何解决这个问题？

Value From Postman
- Plandate function
http://xxx.xxx.xxx.xx/ProjectService/PODService.svc/GetPlanDate/2
"[  {    \"PlanDate\": \"26/08/2019\",    \"PlanDateFullFormat\": \"20190826\"  },  {    \"PlanDate\": \"27/08/2019\",    \"PlanDateFullFormat\": \"20190827\"  }]"

- PlanShipment
http://xxx.xxx.xxx.xx/ProjectService/PODService.svc/GetShipment/2/20190826
"[  {    \"Shipment\": \"4505023278\"  },  {    \"Shipment\": \"4505023279\"  }]"
http://xxx.xxx.xxx.xx/ProjectService/PODService.svc/GetShipment/2/20190827
"[  {    \"Shipment\": \"4505023244\"  },  {    \"Shipment\": \"4505023274\"  }]"

Return Value From JSON
- Plandate function
http://xxx.xxx.xxx.xx/ProjectService/PODService.svc/GetPlanDate/2
pplandateCategories ==>["20190826", "20190827"]

- PlanShipment
http://xxx.xxx.xxx.xx/ProjectService/PODService.svc/GetShipment/2/20190827
getpShipmentDCPlanData ==>["4505023244", "4505023274"]

Swift
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
      return 2
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        if component == 0 {
            return pPlandateCategories.count
        }else{
            let selected = pickerview.selectedRow(inComponent:0)
           return pShipmentCategories[selected].count ———>. Thread 1: Fatal error: Index out of range
        }
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        if component == 0 {
            return pPlandateCategories[row]
        }else{
            let selected = pickerview.selectedRow(inComponent:0)
            return pShipmentCategories[selected][row]
        }
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        if component == 0{
            pickerview.reloadComponent(1)

        }else{
            let selected = pickerview.selectedRow(inComponent:0)
//            getpPlanDatePickerView.text = "PlanDate:" + " " + pplandateCategories[selected][row]
            someTextField.text = "Shipment:" + " " + pShipmentCategories[selected][row]
        }
    }

Error when Run Project 
My WebService ==> http://xxx.xxx.xxx.xx/ProjectService/PODService.svc/GetPlanDate/2GetPlanDate/2
Fatal error: Index out of range
2019-12-19 10:55:14.459056+0700 pickerDateAndShipment[782:19020] Fatal error: Index out of range

Answer 1

只有在异步加载组件的数据并且在第一次重新加载表视图时数据源为空时才会发生崩溃。

为了避免崩溃检查pShipmentCategories数组是否为空

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    if component == 0 {
        return pPlandateCategories.count
    } else {
        let selected = pickerview.selectedRow(inComponent:0)
        return pShipmentCategories.isEmpty ? 0 : pShipmentCategories[selected].count
    }
}