不符合UIPickerViewDataSource协议

Question

我不知道我的密码有什么问题。我试着遵循这个教程，但是同样的错误也会发生。

错误：

类型'FourthViewController‘不符合协议'UIPickerViewDataSource’

这是我的代码：

import UIKit

let characters = ["Jaja Bink", "Luke", "Han Solo", "Princess Leia"];

let weapons = ["LightSaber", "Pistol", "Keris"];

class FourthViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

    @IBOutlet weak var doublePicker: UIPickerView!

    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.
    }

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


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

        if component == 0 {
            return characters[row]
        } else {
            return weapons[row]
        }

    }

    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int? {
        if component == 0 {
            return characters.count
        } else {
            return weapons.count
        }
    }

}

Answer 1

如果您使用的是UIPickerViewDataSource，则可以替换协议Swift 3的不推荐版本。

协议不推荐的方法

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

Swift 3 3协议的最新方法

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

注意:对于其他所需的协议方法，也是相同的。i.e

被反对的：

func pickerView(pickerView: UIPickerView!, numberOfRowsInComponent component: Int) -> Int

最新版本：

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int

Answer 2

因为所需的委托方法不正确。

代之以：

func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {

    if component == 0 {
        return characters.count
    } else {
        return weapons.count
    }
}

委托方法返回不正确的Int?。

Answer 3

您必须实现它的功能：

func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int 
func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int