SwiftUI: Published string changes inside view model are not updating view - swift

Question

I have a timer inside my view model class which every second changes two #Published strings inside the view model. View model class is an Observable Object which Observed by the view but the changes to these string objects are not updating my view.
I have a very similar structure in many other views(Published variables inside a ObservableObject which is observed by view) and it always worked. I can't seem to find what am I doing wrong?
ViewModel
final class QWMeasurementViewModel: ObservableObject {
#Published var measurementCountDownDetails: String = ""
#Published var measurementCountDown: String = ""
private var timer: Timer?
private var scheduleTime = 0
func setTimer() {
timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in
DispatchQueue.main.async {
self.scheduleTime += 1
if self.scheduleTime == 1 {
self.measurementCountDownDetails = "Get ready"
self.measurementCountDown = "1"
}
else if self.scheduleTime == 2 {
self.measurementCountDownDetails = "Relax your arm"
self.measurementCountDown = "2"
}
else if self.scheduleTime == 3 {
self.measurementCountDownDetails = "Breathe"
self.measurementCountDown = "3"
}
else if self.scheduleTime == 4 {
self.measurementCountDownDetails = ""
self.measurementCountDown = ""
timer.invalidate()
}
}
}
}
}
View
struct QWMeasurementView: View {
#ObservedObject var viewModel: QWMeasurementViewModel
var body: some View {
VStack {
Text(viewModel.measurementCountDownDetails)
.font(.body)
Text(viewModel.measurementCountDown)
.font(.title)
}
.onAppear {
viewModel.setTimer()
}
}
}
Edit
After investigation, this seems to be related to how it is being presented. Cause if it's a single view this code works but I am actually presenting this as a sheet. (Still cannot understand why would it make a difference..)
struct QWBPDStartButtonView: View {
#ObservedObject private var viewModel: QWBPDStartButtonViewModel
#State private var startButtonPressed: Bool = false
init(viewModel: QWBPDStartButtonViewModel) {
self.viewModel = viewModel
}
var body: some View {
Button(action: {
self.startButtonPressed = true
}) {
ZStack {
Circle()
.foregroundColor(Color("midGreen"))
Text("Start")
.font(.title)
}
}
.buttonStyle(PlainButtonStyle())
.sheet(isPresented: $startButtonPressed) {
QWMeasurementView(viewModel: QWMeasurementViewModel())
}
}
}

Answer 1

You’re passing in a brand new viewmodel to the sheet’s view.
Try passing in the instance from line 3