我正在构建一个UIPickerView，与我们在帖子中非常相似 3 Component Dynamic Multi UIPickerView Swift。

我的代码是

国家/地区

import UIKit

class Country { 
var name: String 
var cities: [City]

init(name:String,cities:[City]) {
    self.name = name
    self.cities = cities
}
}

Class City

    import UIKit

class City { 
   var name: String 

init(name:String) {
    self.name = name
}
}

ViewController

class ViewController: UIViewController,UIPickerViewDelegate,UIPickerViewDataSource {

@IBOutlet weak var pickerView: UIPickerView!
@IBOutlet weak var countryLbl: UILabel!

var countries = [Country]()
var newOrExisting = "New"

override func viewDidLoad() {

    pickerView.delegate = self
    pickerView.dataSource = self

    countries.append(Country(name: "UK",cities: [City(name: "London"),City(name: "Manchester"),City(name: "Bristol")]))
    countries.append(Country(name: "USA",cities: [City(name: "New York"),City(name: "Chicago")]))
    countries.append(Country(name: "China",cities: [City(name: "Beijing"),City(name: "Shanghai"),City(name: "Shenzhen"),City(name: "Hong Kong")]))

    super.viewDidLoad()
    if newOrExisting == "Existing" {
    // here I need to load existing Country and City to the UIPickerView (for example,USA and Chigado) based on their names
    // newOrExisting status is updated in another ViewController. For example,let's assume it came as "existing"
    }


}

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

func pickerView(_ pickerView: UIPickerView,numberOfRowsInComponent component: Int) -> Int {

    if component == 0 {
        return countries.count
    } else  {
        let selectedCountry = pickerView.selectedRow(inComponent: 0)
        return countries[selectedCountry].cities.count
    } 
}

func pickerView(_ pickerView: UIPickerView,titleForRow row: Int,forComponent component: Int) -> String? {
    if component == 0 {
        return countries[row].name
    } else {
        let selectedCountry = pickerView.selectedRow(inComponent: 0)
        return countries[selectedCountry].cities[row].name
    } 
}

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

    let selectedCountry = pickerView.selectedRow(inComponent: 0)
    let selectedCity = pickerView.selectedRow(inComponent: 1)
    let cityR = countries[selectedCountry].cities[selectedCity].name

    countryLbl.text = "The right answer was: \(selectedCountry) in \(cityR)"

}
}

注意：我之所以没有在此处添加评论，是因为我的声誉不到50个，因此无法发表评论。

使用上面的代码，我可以将数据添加到UIPickerView并从中读取数据。 然后，我将该数据存储到Firebase数据库中。例如，我在那里会有国家名称“ USA”和城市名称“ Chicago”。

但是，我现在需要走相反的道路。如果我从数据库中读取了“美国”和“芝加哥”，如何仅使用名称在UIPickerView中选择它们？我的数据库中没有索引。 有办法吗？

谢谢