swift - 如何用字典填充选择器 View ？

Question

我想用字典填充选择器，但在设置行标题时遇到了问题。

基本上我的选择器应该有 2 个组件，如下所示

|Alabama| ---> ["35010", "35011","35012"]
|Arizona| ---> ["99501", "99502"]
|California|--> ["90001", "90002", "90003"]

第一个选择器应该有状态，第二个选择器应该根据状态有不同的值。我已将组件数设置为两个，创建了一个字典，其中状态作为键，代码作为组件值，但我无法在选择器中填充值。

 class dependentPicker: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {



     @IBOutlet weak var dependentPicker: UIPickerView!

        let stateToPostalCodeDB = [
            "Alabama" :[ "35010","35011","35012"]
            "Arizona" : [ "85001", "85002"],
            "California": [ "90001","90002","90003"]]

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
            return 2
        }
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
            //
            }
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {

            //

        }

我可以用两个选择器来解决这个问题，但我想知道如何用两个组件和字典来解决这个问题。我基本上想学习如何使用字典填充选择器。

Answer 1

您最好创建一个结构来保存各州及其邮政编码。字典很快就会变得困惑。无论如何，这是代码。请参阅其中的评论。

class ViewController: UIViewController {
    @IBOutlet weak var pickerView: UIPickerView!
    var stateToPostalCodeDB = [
        "Alabama": ["35010", "35011","35012"],
        "Arizona": ["99501", "99502"],
        "California": ["90001", "90002", "90003"]
    ]

    /// The keys in a dictionary are unordered
    /// Create a computed property that sorts the states alphabetically
    var states: [String] { return stateToPostalCodeDB.keys.sorted() }

    override func viewDidLoad() {
        super.viewDidLoad()
        pickerView.dataSource = self
        pickerView.delegate = self
    }
}

/// An enum to define the columns of the UIPickerView
/// Better than using 0 or 1 or any mysterious number
private enum PickerViewComponents: Int, CaseIterable {
    case state, zipCode
}

/// The data source and delegate of the Picker View
extension ViewController: UIPickerViewDataSource, UIPickerViewDelegate {
    /// The number of columns of the Picker View
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return PickerViewComponents.allCases.count
    }

    /// The number of rows for each columns
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        let componentName = PickerViewComponents.allCases[component]
        switch componentName {
        case .state:
            return states.count
        case .zipCode:
            let index = pickerView.selectedRow(inComponent: PickerViewComponents.state.rawValue)
            let state = states[index]
            return stateToPostalCodeDB[state]!.count
        }
    }

    /// The label for each row
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        let componentName = PickerViewComponents.allCases[component]
        switch componentName {
        case .state:
            return states[row]
        case .zipCode:
            let index = pickerView.selectedRow(inComponent: PickerViewComponents.state.rawValue)
            let state = states[index]
            return stateToPostalCodeDB[state]?[row]
        }
    }

    /// If the user changes the state, reload the zip codes
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        let componentName = PickerViewComponents.allCases[component]
        if componentName == .state {
            let zipCode = PickerViewComponents.zipCode.rawValue
            pickerView.reloadComponent(zipCode)
            pickerView.selectRow(0, inComponent: zipCode, animated: true)
        }
    }
}