不符合协议"UIPickerViewDataSource“

Question

为什么视图控制器不符合UIPickerViewDataSource？

我已经检查了所有我能做的事情，以便从网络上调试它。

我已经为协议键入了所有必要的函数(Swift 3.1)，但都是徒劳的。

下面是我的代码：

class SelectClassViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
    let grades = ["7", "8", "9", "10", "11", "12"]

    var selectCurrentGrade : String? = nil

    @IBOutlet weak var Grade: UIPickerView!

    @IBAction func Next(_ sender: Any) {
        if selectCurrentGrade != nil {
            performSegue(withIdentifier: "GradeToClass", sender: self)
        }
    }

    @IBAction func Back(_ sender: Any) {
        performSegue(withIdentifier: "GradeToMain", sender: self)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

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

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

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

        func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
            selectCurrentGrade = grades[row]
        }
    }
}

Answer 1

你的函数在viewDidLoad里面，把它们移到外面就行了