Timer within EnvironmentObject view model not updating the View - mvvm

Question

I have a view model, that has multiple child view models. I am fairly new to watchOS, SwiftUI and Combine - taking this opportunity to learn.
I have a watchUI where it has
Play Button (View) - SetTimerPlayPauseButton
Text to show Time (View) - TimerText
View Model - that has 1 WatchDayProgramViewModel - N: ExerciseTestClass - N: SetInformationTestClass. For each ExerciseSets, there is a watchTimer & watchTimerSubscription and I have managed to run the timer to update remaining rest time.
ContentView - that has been injected the ViewModel as EnvironmentObject
If I tap SetTimerPlayPauseButton to start the timer, timer is running, working and changing the remainingRestTime(property within the child view model SetInformationTestClass) correctly, but the updates/changes are not being "published" to the TimerText View.
I have done most, if not all, the recommendation in other SO answers, I even made all my WatchDayProgramViewModel and ExerciseTestClass,SetInformationTestClass properties #Published, but they are still not updating the View, when the view model properties are updated as shown in the Xcode debugger below.
Please review my code and give me some advice on how to improve it.
ContentView
struct ContentView: View {
#State var selectedTab = 0
#StateObject var watchDayProgramVM = WatchDayProgramViewModel()
var body: some View {
TabView(selection: $selectedTab) {
SetRestDetailView().id(2)
}
.environmentObject(watchDayProgramVM)
.tabViewStyle(PageTabViewStyle())
.indexViewStyle(.page(backgroundDisplayMode: .automatic))
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
Group {
ContentView(watchDayProgramVM: WatchDayProgramViewModel())
}
}
}
SetRestDetailView
import Foundation
import SwiftUI
import Combine
struct SetRestDetailView: View {
#EnvironmentObject var watchDayProgramVM: WatchDayProgramViewModel
var setCurrentHeartRate: Int = 120
#State var showingLog = false
var body: some View {
HStack {
let elapsedRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].elapsedRestTime
let totalRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].totalRestTime
TimerText(elapsedRestTime: elapsedRestTime, totalRestTime: totalRestTime, rect: rect)
.border(Color.yellow)
}
HStack {
SetTimerPlayPauseButton(isSetTimerRunningFlag: false,
playImage: "play.fill",
pauseImage: "pause.fill",
bgColor: Color.clear,
fgColor: Color.white.opacity(0.5),
rect: rect) {
print("playtimer button tapped")
self.watchDayProgramVM.exerciseVMList[0].sets[2].startTimer()
let elapsedRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].elapsedRestTime
let totalRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].totalRestTime
print("printing elapsedRestTime from SetRestDetailView \(elapsedRestTime)")
print("printing elapsedRestTime from SetRestDetailView \(totalRestTime)")
}
.border(Color.yellow)
}
}
}
TimerText
struct TimerText: View {
var elapsedRestTime: Int
var totalRestTime: Int
var rect: CGRect
var body: some View {
VStack {
Text(counterToMinutes())
.font(.system(size: 100, weight: .semibold, design: .rounded))
.kerning(0)
.fontWeight(.semibold)
.minimumScaleFactor(0.25)
.padding(-1)
}
}
func counterToMinutes() -> String {
let currentTime = totalRestTime - elapsedRestTime
let seconds = currentTime % 60
let minutes = Int(currentTime / 60)
if currentTime > 0 {
return String(format: "%02d:%02d", minutes, seconds)
}
else {
return ""
}
}
}
ViewModel
import Combine
final class WatchDayProgramViewModel: ObservableObject {
#Published var exerciseVMList: [ExerciseTestClass] = [
(static/hard-coded values for testing)
]
class ExerciseTestClass: ObservableObject {
init(exercise: String, sets: [SetInformationTestClass]) {
self.exercise = exercise
self.sets = sets
}
var exercise: String
#Published var sets: [SetInformationTestClass]
}
class SetInformationTestClass: ObservableObject {
init(totalRestTime: Int, elapsedRestTime: Int, remainingRestTime: Int, isTimerRunning: Bool) {
self.totalRestTime = totalRestTime
self.elapsedRestTime = elapsedRestTime
self.remainingRestTime = remainingRestTime
self.isTimerRunning = isTimerRunning
}
#Published var totalRestTime: Int
#Published var elapsedRestTime: Int
#Published var remainingRestTime: Int
#Published var isTimerRunning = false
#Published var watchTimer = Timer.publish(every: 1.0, on: .main, in: .default)
#Published var watchTimerSubscription: AnyCancellable? = nil
#Published private var startTime: Date? = nil
func startTimer() {
print("startTimer initiated")
self.watchTimerSubscription?.cancel()
if startTime == nil {
startTime = Date()
}
self.isTimerRunning = true
self.watchTimerSubscription = watchTimer
.autoconnect()
.sink(receiveValue: { [weak self] _ in
guard let self = self, let startTime = self.startTime else { return }
let now = Date()
let elapsedTime = now.timeIntervalSince(startTime)
self.remainingRestTime = self.totalRestTime - Int(elapsedTime)
self.elapsedRestTime = self.totalRestTime - self.remainingRestTime
guard self.remainingRestTime > 0 else {
self.pauseTimer()
return
}
self.objectWillChange.send()
print("printing elapsedRest Time \(self.elapsedRestTime) sec")
print("printing remaining Rest time\(self.remainingRestTime)sec ")
})
}
func pauseTimer() {
//stop timer and retain elapsed rest time
print("pauseTimer initiated")
self.watchTimerSubscription?.cancel()
self.watchTimerSubscription = nil
self.isTimerRunning = false
self.startTime = nil
}

Answer 1

Managed to resolve the issue with help of #lorem ipsum and his feedback. As per his comment, the problem lied with the fact that
it is more than likely not working because you are chaining ObservableObjects #Published will only detect a change when the object is changed as a whole now when variables change. One way to test is to wrap each SetInformationTestClass in an #ObservbleObject by using a subview that takes the object as a parameter.
After which, I managed to find similar SO answers on changes in nested view model (esp child), and made the child view model an ObservedObject. The changes in child view model got populated to the view. Please see the changed code below.
SetRestDetailView
import Foundation
import SwiftUI
import Combine
struct SetRestDetailView: View {
#EnvironmentObject var watchDayProgramVM: WatchDayProgramViewModel
var setCurrentHeartRate: Int = 120
#State var showingLog = false
var body: some View {
HStack {
let elapsedRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].elapsedRestTime
let totalRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].totalRestTime
let setInformatationVM = self.watchDayProgramVM.exerciseVMList[0].sets[2]
TimerText(setInformationVM: setInformatationVM, rect: rect)
.border(Color.yellow)
}
HStack {
SetTimerPlayPauseButton(isSetTimerRunningFlag: false,
playImage: "play.fill",
pauseImage: "pause.fill",
bgColor: Color.clear,
fgColor: Color.white.opacity(0.5),
rect: rect) {
print("playtimer button tapped")
self.watchDayProgramVM.exerciseVMList[0].sets[2].startTimer()
let elapsedRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].elapsedRestTime
let totalRestTime = watchDayProgramVM.exerciseVMList[0].sets[2].totalRestTime
print("printing elapsedRestTime from SetRestDetailView \(elapsedRestTime)")
print("printing elapsedRestTime from SetRestDetailView \(totalRestTime)")
}
.border(Color.yellow)
}
}
}
TimerText
struct TimerText: View {
#ObservedObject var setInformationVM: SetInformationTestClass
// #State var elapsedRestTime: Int
// #State var totalRestTime: Int
var rect: CGRect
var body: some View {
VStack {
Text(counterToMinutes())
.font(.system(size: 100, weight: .semibold, design: .rounded))
.kerning(0)
.fontWeight(.semibold)
.minimumScaleFactor(0.25)
.padding(-1)
}
}
func counterToMinutes() -> String {
let currentTime = setInformationVM.totalRestTime - setInformationVM.elapsedRestTime
let seconds = currentTime % 60
let minutes = Int(currentTime / 60)
if currentTime > 0 {
return String(format: "%02d:%02d", minutes, seconds)
}
else {
return ""
}
}
}