SwiftUI iOS CHARTS: How to get highlighted value

Question

Using iOS Charts (by Daniel Gindi https://github.com/danielgindi/Charts) and SwiftUI, I would like to get the selected value from a Line Chart, the highlighted value when the user tap it. The highlight is working, I can see the additional lines for this value.

After some research, I found we have to create this function: chartValueSelected() but it's never called in this case. I suppose I have to deal with the delegate but I did not find any solution or example with SwiftUI. Can someone help ? Thanks LineChart

    import Foundation
    import Charts
    import SwiftUI

    struct GraphMeterLine : UIViewRepresentable {
    var xArray:[Float] = [0,1,2,3,4]
    var yArray:[Float] = [0,3,6,2,12]
    var data = LineChartData()
    let chartline = LineChartView()

        func makeUIView(context: Context) -> LineChartView {
            return chartline
        }

        func updateUIView(_ uiView: LineChartView, context: Context) {
            //when data changes chartd.data update is required
            uiView.data = createGraph()
        }
    
    
    func createGraph() -> LineChartData {
        var lineChartEntry = [ChartDataEntry]()
       
            for i in 0..<yArray.count {
                let value = ChartDataEntry(x: Double(xArray[i]), y: Double(yArray[i]))
                lineChartEntry.append(value)
            }
            
        let line1 = LineChartDataSet(entries: lineChartEntry, label: "Number")
        

        data.addDataSet(line1)

                data.setDrawValues(false)
                return data
    }

    public func chartValueSelected(_ chartView: ChartViewBase, entry: ChartDataEntry, highlight: Highlight) {
        print("To Display Values X/Y Values here")
    }
    
        typealias UIViewType = LineChartView
        
    }

Denis Kozhukhov · Accepted Answer · 2021-01-16 20:42:53Z

1

Will try another one idea. I can't test it right now, so don't sure it will work, but it builds successfully, try it on your side. There is code I added in your code:

var xArray:[Float] = [0,1,2,3,4]
var yArray:[Float] = [0,3,6,2,12]
var data = LineChartData()
let chartline = LineChartView()

class ChartDelegete: ChartViewDelegate {
    func chartValueSelected(_ chartView: ChartViewBase, entry: ChartDataEntry, highlight: Highlight) {
        print("To Display Values X/Y Values here")
    }
}

let chartDelegete = ChartDelegete()

func makeUIView(context: Context) -> LineChartView {
    chartline.delegate = chartDelegete
    return chartline
}

UPDATED after comment

Old answer

Add delegate to definition

struct GraphMeterLine : UIViewRepresentable, ChartViewDelegate {

and set delegate

chartline.delegate = self

in makeUIView(context: call for example. It should work.

edited Jan 16, 2021 at 20:42

answered Jan 7, 2021 at 11:52

Denis Kozhukhov

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4 Comments

ThomasFr Over a year ago

Thanks for the reply, but this is a struct (UIViewProtocol) I can not add ChartViewDelegate: "Non-class type 'GraphMeterLine' cannot conform to class protocol 'ChartViewDelegate' " I tried different solutions using Class Coordinator inside the struct function but I can not access data as I want. Other idea ?

Denis Kozhukhov Over a year ago

I understand what problem you have. I edited my answer with another idea I cant try right now for work. Try it please. Idea seems strange but maybe can work ^_^

ThomasFr Over a year ago

It worked perfectly fine. I can't believe I got stuck on this for so long time hehe Thanks a lot :)

Taras Over a year ago

worked for me only with Charts v3.6.0

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