Value of type 'ViewController' does not conform to 'ChartViewDelegate' in assignment

Question

I'm using charts api, and getting this error

Value of type 'ViewController' does not conform to 'ChartViewDelegate' in assignment

class RiseAndFallViewController: UIViewController,ChartViewDelegate {
    func chartValueSelected(chartView: ChartViewBase, entry: ChartDataEntry, dataSetIndex: Int, highlight: Highlight) {
        print("")
    }

    @IBOutlet weak var RiseAndFall: HorizontalBarChartView!
    override func viewDidLoad() {
        RiseAndFall.delegate = self
    }
}

this is my code, and I'm getting above error, could you help me?