斯威夫特 - 级联选择器

Question

假设我有3个采摘者，其中包含以下内容：

 Restaurant{
   [Menu]
    name
 }

 Menu{
  [Ingredients]
  time
 }

 Ingredients{
  ...
 }

如果对象发生变化，如何实现自动更新的选择器？ （例如，当餐厅被挑选时，其菜单和成分会发生变化，当选择菜单时，成分会发生变化）

Answer 1

您可以这样做：

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate
{
    @IBOutlet weak var restaurantsPicker: UIPickerView!
    @IBOutlet weak var menuPicker: UIPickerView!
    @IBOutlet weak var ingredientsPicker: UIPickerView!

    var restaurants = ["R1", "R2", "R3"]

    var menus = ["R1": ["M1", "M2"],
                "R2": ["M2"],
                "R3": ["M1", "M3"]]

    var ingredients = ["M1":["I1", "I2", "I3"],
                       "M2":["I1", "I3"],
                       "M3":["I2", "I3"]]


    func numberOfComponents(in pickerView: UIPickerView) -> Int
    {
        return 1
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int
    {
        if pickerView === restaurantsPicker
        {
            return restaurants.count
        }
        else if pickerView === menuPicker
        {
            let restaurant = restaurants[restaurantsPicker.selectedRow(inComponent: 0)]
            return menus[restaurant]!.count
        }
        else
        {
            let restaurant = restaurants[restaurantsPicker.selectedRow(inComponent: 0)]
            let menu = menus[restaurant]![menuPicker.selectedRow(inComponent: 0)]
            return ingredients[menu]!.count
        }
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?
    {
        if pickerView === restaurantsPicker
        {
            return restaurants[row]
        }
        else if pickerView === menuPicker
        {
            let restaurant = restaurants[restaurantsPicker.selectedRow(inComponent: 0)]
            return menus[restaurant]?[row]
        }
        else
        {
            let restaurant = restaurants[restaurantsPicker.selectedRow(inComponent: 0)]
            let menu = menus[restaurant]![menuPicker.selectedRow(inComponent: 0)]
            return ingredients[menu]?[row]
        }
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
    {
        if pickerView === restaurantsPicker
        {
            menuPicker.reloadComponent(0)
            ingredientsPicker.reloadComponent(0)
        }
        else if pickerView === menuPicker
        {
            ingredientsPicker.reloadComponent(0)
        }
    }
}

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