How to add tap gesture recognition in Swift3 IOS Pie chart?

Question

I am in mid of developing small practice IOS app using Swift 3. Inside that app, I would like to have a Pie chart. To build a Pie chart, I followed this link and pie chart is getting generated.

Now I want to add one more functionality. When user tap on one of the area of Pie chart like any month, then it should open a new controller and display details of that month only.

I managed to add gesture recognition functionality. But when I tap any portion of the screen, it opens up the new screen. I want to limit that tap functionality to Pie chart section only and that Pie chart month should be captured. The code is

let gestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(self.handleTap))

pieChartView.addGestureRecognizer(gestureRecognizer)

And handle tap code is

func handleTap(gestureRecognizer: UIGestureRecognizer) {
let monthDetail = storyboard?.instantiateViewController(withIdentifier: "MonthTableView") as! MonthDetailsTableViewController
monthDetail = month  //Should be the month value of Tap area
navigationController?.pushViewController(monthDetail, animated: true)

}

Appreciate any help!!

==========================

Updated Code

import UIKit
import Charts
import CoreData

class ExpenseViewController: UIViewController, ChartViewDelegate {

@IBOutlet weak var pieChartView: PieChartView!

    let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]
    var unitsSold = [10.0, 20.0, 10.0, 30.0, 10.0, 10.0]

     override func viewDidLoad() {
        super.viewDidLoad()

        setChart(dataPoints: months, values: unitsSold)

        pieChartView.delegate = self
     }

     func setChart(dataPoints: [String], values: [Double]) {
        var dataEntries: [ChartDataEntry] = []

        for i in 0..<dataPoints.count {
            let dataEntry = PieChartDataEntry(value: values[i], label: dataPoints[i])
            dataEntries.append(dataEntry)
        }


        let pieChartDataSet = PieChartDataSet(values: dataEntries, label: "Units Sold")
        let pieChartData = PieChartData(dataSet: pieChartDataSet)

        pieChartView.data = pieChartData

      }

     func chartValueSelected(chartView: ChartViewBase, entry: ChartDataEntry, dataSetIndex: Int, highlight: ChartHighlighter) {
        //print("\(entry.value) in \(months[entry.xIndex])")
        print("Y = \(entry.y) ")
        print("X = \(entry.x) ")
    }

}

Answer 1

Check the Touch Events part in your Appcoda tutorial , you find the ChartViewDelegate method chartValueSelected , so you need to use that method instead of UITapGestureRecognizer .

func chartValueSelected(_ chartView: ChartViewBase, entry: ChartDataEntry, highlight: Highlight) {
     print("\(entry.value) in \(yourArray[entry.xIndex])")
}

Answer 2

在handleTap ，使用手势识别器的locationInView来确定水龙头所在的图表部分（如果有的话），并做出相应的响应。