SwiftUICharts are not redrawn when given new data - swiftui

Question

I am adding the possibility to swipe in order to update a barchart. What I want to show is statistics for different station. To view different station I want the user to be able to swipe between the stations. I can see that the swiping works and each time I swipe I get the correct data from my controller. The problem is that my view is not redrawn properly.
I found this guide, but cannot make it work.
Say I swipe right from station 0 with data [100, 100, 100] to station 2, the retrieved data from my controller is [0.0, 100.0, 0.0]. The view I have still is for [100, 100, 100]`.
The station number is correctly updated, so I suspect it needs some state somehow.
Here is the code:
import SwiftUI
import SwiftUICharts
struct DetailedResultsView: View {
#ObservedObject var viewModel: ViewModel = .init()
#State private var tabIndex: Int = 0
#State private var startPos: CGPoint = .zero
#State private var isSwiping = true
var body: some View {
VStack {
Text("Station \(viewModel.getStation() + 1)")
TabView(selection: $tabIndex) {
BarCharts(data: viewModel.getData(kLatestRounds: 10, station: viewModel.getStation()), disciplineName: viewModel.getName()).tabItem { Group {
Image(systemName: "chart.bar")
Text("Last 10 Sessions")
}}.tag(0)
}
}.gesture(DragGesture()
.onChanged { gesture in
if self.isSwiping {
self.startPos = gesture.location
self.isSwiping.toggle()
}
}
.onEnded { gesture in
if gesture.location.x - startPos.x > 10 {
viewModel.decrementStation()
}
if gesture.location.x - startPos.x < -10 {
viewModel.incrementStation()
}
}
)
}
}
struct BarCharts: View {
var data: [Double]
var title: String
init(data: [Double], disciplineName: String) {
self.data = data
title = disciplineName
print(data)
}
var body: some View {
VStack {
BarChartView(data: ChartData(points: self.data), title: self.title, style: Styles.barChartStyleOrangeLight, form: CGSize(width: 300, height: 400))
}
}
}
class ViewModel: ObservableObject {
#Published var station = 1
let controller = DetailedViewController()
var isPreview = false
func getData(kLatestRounds: Int, station: Int) -> [Double] {
if isPreview {
return [100.0, 100.0, 100.0]
} else {
let data = controller.getResults(kLatestRounds: kLatestRounds, station: station, fileName: userDataFile)
return data
}
}
func getName() -> String {
controller.getDiscipline().name
}
func getNumberOfStations() -> Int {
controller.getDiscipline().getNumberOfStations()
}
func getStation() -> Int {
station
}
func incrementStation() {
station = (station + 1) % getNumberOfStations()
}
func decrementStation() {
station -= 1
if station < 0 {
station = getNumberOfStations() - 1
}
}
}
The data is printed inside the constructor each time I swipe. Shouldn't that mean it should be updated?

Answer 1

I don’t use SwiftUICharts so I can’t test it, but the least you can try is manually set the id to the view
struct DetailedResultsView: View {
#ObservedObject var viewModel: ViewModel = .init()
#State private var tabIndex: Int = 0
#State private var startPos: CGPoint = .zero
#State private var isSwiping = true
var body: some View {
VStack {
Text("Station \(viewModel.getStation() + 1)")
TabView(selection: $tabIndex) {
BarCharts(data: viewModel.getData(kLatestRounds: 10, station: viewModel.getStation()), disciplineName: viewModel.getName())
.id(viewmodel.station) // here. If it doesn’t work, you can set it to the whole TabView
.tabItem { Group {
Image(systemName: "chart.bar")
Text("Last 10 Sessions")
}}.tag(0)
}
}.gesture(DragGesture()
.onChanged { gesture in
if self.isSwiping {
self.startPos = gesture.location
self.isSwiping.toggle()
}
}
.onEnded { gesture in
if gesture.location.x - startPos.x > 10 {
viewModel.decrementStation()
}
if gesture.location.x - startPos.x < -10 {
viewModel.incrementStation()
}
}
)
}
}