Question

我在一个类中有一个对象数组，并试图将该数组引用为UIPickerView，但是当点击UITextField时，它崩溃并返回nil。当在countryInput文本字段上点击时，它应该显示带有“日本摩纳哥”的pickerview，依此类推...关于我在做什么的任何想法吗？预先谢谢你。

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

您只声明selectionData而不声明instantiateViewController，这就是它发生的原因。

override func viewDidLoad() {
    super.viewDidLoad()
    selectionData = self.storyboard?.instantiateViewController(withIdentifier: "SelectionViewController") as! SelectionViewController
    picker.dataSource = self
    picker.delegate = self
}

Answer 2

我认为甚至不需要使用SelectionViewController的整个实例作为dataSource到UIPickerView的地方。

相反，您可以简单地在[LifeClass]中创建SetupViewController数组并在那里使用它。

 class SetupViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {
    private var lifeArr = [LifeClass]()

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

    private func populateArray() {
        let monaco = LifeClass()
        monaco.country = "Monaco"
        monaco.male = 85.6
        monaco.female = 93.5
        lifeArr.append(monaco)

        let japan = LifeClass()
        japan.country = "Japan"
        japan.male = 81.9
        japan.female = 88.8
        lifeArr.append(japan)
    }

    //Rest of the code...
}

在UIPickerViewDataSource和UIPickerViewDelegate方法中，使用

self.lifeArr

代替

selectionData.lifeArr

Answer 3

创建一个新类以保留此数据，并在需要访问它的任何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]
  }

}

例如从SetupViewController最高层：-

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
}

数组返回null并崩溃

3 个答案: