类型'x‘不符合'UIPickerViewDataSource’协议

Question

    import UIKit

class FourthViewController: UIViewController,UIPickerViewDelegate,UIPickerViewDataSource {


    @IBOutlet weak var picker: UIPickerView!

      var pickerData: [String] = [String]()


    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.

        self.picker.delegate = self
        self.picker.dataSource = self

        pickerData = ["Item 1", "Item 2", "Item 3", "Item 4", "Item 5", "Item 6"]    }

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

    //MARK: - Delegates and data sources
    //MARK: Data Sources
    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
        return 1
    }
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return pickerData.count
    }

    //MARK: Delegates
    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return pickerData[row]
    }
    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

错误:键入“FourthViewController”不符合协议“UIPickerViewDataSource”

只是为了测试一些特性，但我不明白问题所在

Answer 1

正如您已经发现的，您需要实现numberOfComponents(in:)。

您的numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int需要更改为：

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

此外，您还需要修改pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?。

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

在Swift 3中，许多方法被重命名。检查最新参考，小心这。你最好把Xcode版本写在你的问题上。

Answer 2

您必须遵守数据源协议：

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

试试下面的代码：

//MARK: - Delegates and data sources
        //MARK: Data Sources
        public 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]
        }

Answer 3

如果在UIPickerViewDataSource中确认该协议，则必须实现swift和UIPickerViewDelegate所需的所有方法。否则会在编译时产生错误。