arrays - 数组返回 null 并崩溃

Question

我在一个类中有一个对象数组，并试图将该数组引用到 UIPickerView，但是当 UITextField 被点击时，它崩溃并返回 nil。当点击 countryInput 文本字段时，它应该显示带有“摩纳哥，日本”等的选择器 View ......关于我做错了什么的任何想法？提前谢谢你。

class SelectionViewController: UIViewController {

var lifeArr : [LifeClass] = []

let picker = UIPickerView()

    override func viewDidLoad() {
    super.viewDidLoad()     

    let Monaco = LifeClass()
    Monaco.country = "Monaco"
    Monaco.male = 85.6
    Monaco.female = 93.5

    let Japan = LifeClass()
    Japan.country = "Japan"
    Japan.male = 81.9
    Japan.female = 88.8

    lifeArr = [Monaco, Japan]
  }

}


class SetupViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

@IBOutlet weak var birthDayInput: UITextField!
@IBOutlet weak var countryInput: UITextField!

var selectionData : SelectionViewController!
var picker = UIPickerView()

    override func viewDidLoad() {
    super.viewDidLoad()

        picker.dataSource = self
        picker.delegate = self

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

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return selectionData.lifeArr.count
}

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    return selectionData.lifeArr[row].country
}
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    countryInput.text = selectionData.lifeArr[row].country
}



}

Answer 1

创建一个新类来保存这些数据，并在任何需要访问它的 VC 中使用它。例如

class LifeClassDatabase
{
  var lifeArr : [LifeClass] = []

  init() 
  {
    let Monaco = LifeClass()
    Monaco.country = "Monaco"
    Monaco.male = 85.6
    Monaco.female = 93.5

    let Japan = LifeClass()
    Japan.country = "Japan"
    Japan.male = 81.9
    Japan.female = 88.8

    lifeArr = [Monaco, Japan]
  }

}

从例如SetupViewController 顶级:-

private var lifeClassDatabase = LifeClassDatabase()

然后在您的数据源代码中使用它，例如:

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return lifeClassDatabase.lifeArr.count
}