swift - 无法将类型 '[String]' 的返回表达式转换为返回类型 'String?'/UIPickerView

Question

我正在使用 UIPickerView，它给我错误(无法将类型“[String]”的返回表达式转换为返回类型“String？”/UIPickerView)。这是我的代码。

// where the picker view is set up.
let cubesToWorkWith = ["3X3", "2X2", "4X4", "5X5", "6X6", "7X7", "Skewb", "Square-One"]
let threeByThreeArray = ["OLL", "PLL"]
@IBOutlet weak var pickerViewOutlet: UIPickerView!

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

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    let row = pickerView.selectedRow(inComponent: 0)
    print("this is the pickerView\(row)")

    switch row {
    case 0:
        return threeByThreeArray.count
    default:
        return cubesToWorkWith.count
    }
}
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    switch row {
    case 0:
        return threeByThreeArray[row]
    default:
        return getArrayForRow(row: row)
    }
}
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    cubeSelected = Int16(row)
}
func getArrayForRow(row: Int)  -> [String] {

    switch row {
    case 0:
        return threeByThreeArray
    default:
        return cubesToWorkWith
    }

  }
 } 
}

我在“return getArrayForRow(row: row)”处的 titleForRow 内的 switch case 处收到错误感谢您提前提供帮助!!!!

Answer 1

所以你错过了一些东西:

首先，你需要设置delegate ad Datasource为self在 titleForRow 中:

您需要返回一个字符串，以便您:

func getArrayForRow(row: Int)  -> [String]

需要像:

func getArrayForRow(row: Int)  -> String

这是我的报价:

class ViewController: UIViewController ,UIPickerViewDelegate,UIPickerViewDataSource{
// where the picker view is set up.
let cubesToWorkWith = ["3X3", "2X2", "4X4", "5X5", "6X6", "7X7", "Skewb", "Square-One"]
let threeByThreeArray = ["OLL", "PLL"]

@IBOutlet weak var pickerViewOutlet: UIPickerView!


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

    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}



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

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    let row = pickerView.selectedRow(inComponent: 0)
    print("this is the pickerView\(row)")

    switch row {
    case 0:
        return threeByThreeArray.count
    default:
        return cubesToWorkWith.count
    }
}
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    switch row {
    case 0:
        return threeByThreeArray[row] as String
    default:
        return getArrayForRow(row: row) as String
    }
}
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
   // cubeSelected = Int16(row)
}

func getArrayForRow(row: Int)  -> String {

    switch row {
    case 0:
        return threeByThreeArray[row]
    default:
        return cubesToWorkWith[row]
    }

}

}