如何使用UIPicker dataSource

Question

我使用Xcode 8和Swive2.3，但当我尝试使用UIPicker功能时，遇到了一个UIPicker无法工作的问题，这是我的代码：

import UIKit

class ViewController: UIViewController {

    let Num = ["1","2","3","4","5","6"]

    @IBOutlet weak var UIPicker: UIPickerView!
    override func viewDidLoad() {
        super.viewDidLoad()

        func numberOfRows(inComponent component: Int) -> Int {return 1}

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

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

        UIPicker.dataSource = (self as! UIPickerViewDataSource)
        UIPicker.delegate = (self as! UIPickerViewDelegate)
    }

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

当我运行代码时，Xcode警告代码：

无法将“test.ViewController”(0x1000bd8c0)类型的值转换为“UIPickerViewDataSource”(0x1ab289738)。2016-06-29 15:33:35.079300测试474:98176不能将“test.ViewController”(0x1000bd8c0)类型的值投给“UIPickerViewDataSource”(0x1ab289738)。

Answer 1

将UIPickerViewDataSource和UIPickerViewDelegate添加到类声明中：

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate

也不要使用self进行类型铸造

override func viewDidLoad() {
    super.viewDidLoad()

    UIPicker.dataSource = self
    UIPicker.delegate = self
}

此外，还必须将方法移出viewDidLoad函数，并对其进行一些更正：

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

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

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

请注意，我强烈建议您将Num和UIPicker属性重命名为num和picker，这样就不会将它们与类名混在一起。

Upd:完整ViewController代码：

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

    let Num = ["1","2","3","4","5","6"]

    @IBOutlet weak var UIPicker: UIPickerView!
    override func viewDidLoad() {
        super.viewDidLoad()

        UIPicker.dataSource = self
        UIPicker.delegate = self
    }

    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {return 1}
    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {return Num.count}
    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {return Num[row]}
}

Answer 2

import Foundation
import UIKit

class MakeReferralViewController: UITableViewController,UIPickerViewDelegate, UITextFieldDelegate,UIPickerViewDataSource {

    @IBOutlet weak var makeReferralScroll: UIScrollView!

    @IBOutlet weak var userTitleUITextView: UITextField!
    var pickerData = ["Mr.", "Ms.", "Mrs.", "Miss."];
    var picker = UIPickerView()

    override func viewDidLoad() {
        super.viewDidLoad()
        picker.delegate = self
        picker.dataSource = self
        userTitleUITextView.inputView = picker

        // 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 textFieldDidBeginEditing(_ textField: UITextField) {
        makeReferralScroll.setContentOffset(CGPoint(x:0,y:250), animated: true)
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true;
    }

    @available(iOS 10.0, *)
    func textFieldDidEndEditing(_ textField: UITextField, reason: UITextFieldDidEndEditingReason) {
        makeReferralScroll.setContentOffset(CGPoint(x:0,y:0), animated: true)
    }


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

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

    //MARK: Delegate
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {

        return pickerData[row]
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
                userTitleUITextView.text = pickerData[row]

    }


}