PickerView只显示“？”

Question

这是我的源代码，我所做的就是在storyBoard上做选择器视图。在此控制器中通过IBOutlet实现contorl+drag。

然而，它只能被汇编成“？”显示在“选择器”视图中。

问题出在哪里？

import UIKit

class SelectViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate{
    var songNames = ["test1","test2","test3"]

    @IBOutlet weak var songPicker: UIPickerView!

    override func viewDidLoad(){ 
        songPicker.delegate = self
        songPicker.dataSource = self

    }

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

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

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int) -> String? {
        return songNames[row]
    }
}

Answer 1

您忽略了forComponent方法中的dataSource参数。将其添加到titleForRow函数中，如下所示：

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    return songNames[row]
}

这应该能解决你遇到的问题。