Chart does not refresh on State change

[USBA]

My enter view refreshes on @State change except the chart.

@State var component: Calendar.Component = .month
@State var periodCount: Int = 0

The chart does not refresh until I drag on it.

Screen.Recording.2021-02-03.at.7.59.39.PM.mov

LineChart()
           .touchOverlay()
           .xAxisGrid()
           .yAxisGrid()
           .xAxisLabels()
           .yAxisLabels()
           .environmentObject(
                      ChartData(dataPoints : chartDataPoints(periodChange: periodCount, periodComponent: component) )
            )
            .frame(height: horizontalSizeClass == .compact ? 200 : 250)
            .padding()

Please fix this.
Thanks so much for this amazing SwiftUI library.

[willdale]

Hi,

I believe this is because the data being passed into the environmentObject is not @State. This means that a change of the datas state won't cause the views state to change.

While I don't know what the function chartDataPoints() does, I've make one that returns [ChartDataPoint] .

There maybe a more elegant solution but without more info I don't know.

    @Environment(\.horizontalSizeClass) var horizontalSizeClass
    @State var component: Calendar.Component = .month
    @State var periodCount: Int = 0

    // make data a `@State` variable  
    @State var data = ChartData(dataPoints: [])

    var body: some View {
        VStack {
            LineChart()
                .touchOverlay()
                .xAxisGrid()
                .yAxisGrid()
                .xAxisLabels()
                .yAxisLabels()
                .environmentObject(data)
                .padding()
            
            Button(action: {
                periodCount += 1
            }, label: {
                Text("Increment")
            })
        }
        // Re-Initialise data at `onAppear`
        .onAppear {
            data.dataPoints = chartDataPoints(periodChange: periodCount, periodComponent: component)
        }
        // detect changes
        .onChange(of: periodCount, perform: { value in
            data.dataPoints = chartDataPoints(periodChange: value, periodComponent: component)
        })
    }
    
    func chartDataPoints(periodChange: Int, periodComponent: Calendar.Component) -> [ChartDataPoint] {
        var test : [ChartDataPoint] = []
        let one : Double = Double(periodChange + 1)
        let two : Double = Double(periodChange + 4)
        for _ in 1...6 {
            let value = Double.random(in: one...two)
            test.append(ChartDataPoint(value: value))
        }
        return test
    }

Screen.Recording.2021-02-03.at.17.44.30.mov

[USBA]

This works. Thanks so much for the quick reply @willdale