如何在单个选择器中管理国家/州/城市

Question

如何使用单一选择器Objective-C管理国家/州/城市值？

当我尝试它时，它会在索引更改时崩溃。 它适用于城市和州，但与城市有关。哪个库会更好？

请参阅下面的代码

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
     self.txtOfficeLocation.text = self.provinceArray[row]; 
     for (int i = 0; i < self.provinceKeyValueDic.count; i++) {
        if ([self.provinceKeyValueDic.allKeys[i] isEqualToString:self.provinceArray[row]]){
                 provinceID = [[self.provinceKeyValueDic.allValues[i]valueForKey:@"id"]in‌​tegerValue]; NSLog(@"province key :%d", provinceID); 
        }
     }
 }

Answer 1

我知道

你要求Objective-C代码，但这里有一个快速的例子 - 关键元素很容易翻译。

我不知道您是如何设置数据的，但我创建了这样的数据

    struct StateData
{
    var state : String
    var city : [String] = []
}
struct CountryData
{
    var country : String
    var state : [StateData] = []
}
var pickerData : [CountryData] = []

您可以按照自己喜欢的任何方式填充它

    var stateData = CountryData(country: "UK", state: [StateData(state: "Midlothian", city: ["Edinburgh", "Bathgate", "Livingston"])])
    stateData.state.append(StateData(state: "Strathclyde", city: ["Glasgow", "Prestwick", "Lanark"]))
    pickerData.append(stateData)
    stateData = CountryData(country: "USA", state: [StateData(state: "Alabama", city: ["Montgomery", "Birmingham"])])
    stateData.state.append(StateData(state: "Alaska", city: ["Juneau", "Anchorage"]))
    stateData.state.append(StateData(state: "Arizona", city: ["Phoenix", "Another city", "City 3"]))
    pickerData.append(stateData)

我认为关键是要跟踪您选择的内容

var countrySelected : Int   = 0
var stateSelected : Int     = 0
var citySelected : Int      = 0

选取器视图方法需要如下所示

func numberOfComponents(in pickerView: UIPickerView) -> Int
{
    return 3 // country, state, city
}
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int
{
    switch component
    {
    case 0: // country
        return pickerData.count
    case 1: // state
        return pickerData[countrySelected].state.count
    case 2: // city
        return pickerData[countrySelected].state[stateSelected].city.count
    default:
        return 0
    }
}
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?
{
    switch component
    {
    case 0: // country
        return pickerData[row].country
    case 1: // state
        return pickerData[countrySelected].state[row].state
    case 2: // city
        return pickerData[countrySelected].state[stateSelected].city[row]
    default:
        return ""
    }
}

有趣的是，当您更改国家/地区或州时，您最终不会得到指向新显示中不存在的值的州或城市索引 - 就像当您从一个州中选择第三个城市并移动到只有两个城市的州一样。 这将生成您一直看到的越界错误。 你可以这样修复它

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
{
    switch component {
    case 0: // country
        countrySelected = pickerView.selectedRow(inComponent: 0)
        stateSelected = 0
        citySelected = 0
        pickerView.reloadComponent(1)
        pickerView.selectRow(0, inComponent: 1, animated: true)
        pickerView.reloadComponent(2)
        pickerView.selectRow(0, inComponent: 2, animated: true)
    case 1: // country
        stateSelected = pickerView.selectedRow(inComponent: 1)
        citySelected = 0
        pickerView.reloadComponent(2)
        pickerView.selectRow(0, inComponent: 2, animated: true)
    case 2: // country
        citySelected = pickerView.selectedRow(inComponent: 2)
    default:
        break
    }
    print("(pickerData[countrySelected].country), (pickerData[countrySelected].state[stateSelected].state), (pickerData[countrySelected].state[stateSelected].city[citySelected])")
}