Swift中的第一个iOS应用程序-UIPickerView中的问号

我正在开发我的第一个Swift ios应用程序

无法将数据从pickerData获取到我的选择器中，但我只获取问号，而不是实际值。我想这和委托有关，但不确定出了什么问题

import UIKit
import CoreData

class NewWorkoutController: UIViewController,UIPickerViewDelegate, UIPickerViewDataSource {

@IBOutlet weak var workoutDistance: UITextField!

let pickerData = ["11","12","13","14","15"]

// Data Sources
func numberOfComponentsInPickerView(distancePickerView: UIPickerView) -> Int {
    return 1
}
func pickerView(distancePickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return pickerData.count
}
// Delegates
func pickerViewReturnRow(distancePickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
    return pickerData[row]
}
func pickerViewText(distancePickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    workoutDistance.text = pickerData[row]
}
func doneDistancePicker() {
    workoutDistance.resignFirstResponder()
}
func cancelDistancePicker() {
    workoutDistance.resignFirstResponder()
}

@IBAction func textFieldDistanceEditing2(sender: UITextField) {

    // Create picker view
    var distancePickerView: UIPickerView
    distancePickerView = UIPickerView(frame: CGRectMake(0, 200, view.frame.width, 300))
    distancePickerView.backgroundColor = .whiteColor()

    distancePickerView.showsSelectionIndicator = true
    distancePickerView.delegate = self
    distancePickerView.dataSource = self

    // Create toolbar
    var toolBar = UIToolbar()
    toolBar.barStyle = UIBarStyle.Default
    toolBar.translucent = true
    toolBar.tintColor = UIColor(red: 76/255, green: 217/255, blue: 100/255, alpha: 1)
    toolBar.sizeToFit()

    // Create buttons
    var doneButton = UIBarButtonItem(title: "Done", style: UIBarButtonItemStyle.Plain, target: self, action: "doneDistancePicker")
    var spaceButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.FlexibleSpace, target: nil, action: nil)
    var cancelButton = UIBarButtonItem(title: "Cancel", style: UIBarButtonItemStyle.Plain, target: self, action: "cancelDistancePicker")

    // Assign buttons to toolbar
    toolBar.setItems([cancelButton, spaceButton, doneButton], animated: false)
    toolBar.userInteractionEnabled = true

    // Add pickerview and toolbar to textfield
    workoutDistance.inputView = distancePickerView
    workoutDistance.inputAccessoryView = toolBar

    sender.inputView = distancePickerView
}

override func viewDidLoad() {
    super.viewDidLoad()
}
}

---

此函数的签名错误：

func pickerViewReturnRow(distancePickerView: UIPickerView, 
    titleForRow row: Int, 
    forComponent component: Int) -> String!

应该是

func pickerView(pickerView: UIPickerView,
    titleForRow row: Int,
    forComponent component: Int) -> String!

---

因此，该方法（为选择器中的行提供标题）不会被调用。

在所有pickerView委托方法的签名中，您使用不需要的pickerView插座替换了pickerView。您应该修改委托方法主体内的代码，因为如果我们通过编写以下代码将您的pickerView委托和数据源确认为ViewController类，则swift编译器会自动调用委托方法：

pickerViewOutlet.delegate = self
pickerViewOutlet.dataSource = self

---

因此，只需使用默认签名修改所有pickerView委托方法，编译器就会调用它，数据就会显示在其中。

Ah-oh，ReturnRow用于单元格，复制粘贴错误：（非常感谢！可选委托方法的一个问题是，如果方法名称错误，则对象不会以静默方式调用该方法。这会使调试变得困难。请始终记住检查方法名称，然后设置断点（或插入println）并确保确实调用了您的方法。不过，自动完成可能是正确获取方法名称的一个有用的支柱。一旦您声明类符合协议，协议的所有方法都将尝试自动完成，即使是可选的方法。