pickerView 显示为问号而不是数据？

我正在尝试向我的 iphone 应用程序添加一个 pickerview，但它不是显示数组中的字符串，而是显示问号。有谁知道为什么？在过去的一个小时里我一直在试图弄清楚......这是我包含 pickerview 的控制器的代码：

class NewIssueViewController: UIViewController, UIPickerViewDelegate {

    var componentArr = ["component1","component2","component3","component4"]

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.


    }

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

    @IBAction func CancelPressed(sender: AnyObject) {
        self.dismissViewControllerAnimated(true, completion: nil)
    }

    @IBAction func AddPressed(sender: AnyObject) {
        self.dismissViewControllerAnimated(true, completion: nil)
    }

    func numberOfComponentsInPickerView(pickerView: UIPickerView!) -> Int {
        return 1
    }

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

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

您设置了选择器视图的数据源，但没有设置其委托。

因此pickerView:titleForRow:永远不会被叫到。