I have a minimal reproducible example in SwiftUI that demonstrates an issue with view updates when using a class vs a struct. The view updates correctly when using a struct, but it doesn’t update when using a class. Below is the code:

SimpleView.swift

import SwiftUI
import Foundation

struct SimpleView: View {
    @StateObject private var viewModel = SampleViewModel()

    var body: some View {
        VStack {
            Text(viewModel.timeCounter.showerTimeMinutes)
            Button("Update Minutes Class") {
                viewModel.timeCounter.showerTimeMinutes = "15"
            }
            
            VStack {
                Text(viewModel.timeCounterStruct.showerTimeMinutes)
                Button("Update Minutes Struct") {
                    viewModel.timeCounterStruct.showerTimeMinutes = "15"
                }
            }
            
            
            VStack {
                Text(viewModel.timerCounterPublisher.showerTimeMinutes)
                Button("Update Minutes Class with Publisher") {
                    viewModel.timerCounterPublisher.showerTimeMinutes = "15"
                }
            }
        }
    }
}


struct SimpleView_Previews: PreviewProvider {
    static var previews: some View {
        SimpleView()
    }
}

SampleViewModel.swift

class SampleViewModel: ObservableObject {

    @Published var timeCounter = SampleTimeCounter()
    @Published var timeCounterStruct = SampleTimeCounterStruct()
    @Published var timerCounterPublisher = SampleTimeCounterPublihser()
}

// This is support class that will save the shower time for next time.
class SampleTimeCounter {
    var showerTimeMinutes =  "00"
}

class SampleTimeCounterPublihser: ObservableObject {
    @Published var showerTimeMinutes =  "00"
}

struct SampleTimeCounterStruct {
    var showerTimeMinutes =  "00"
}

When I update the showerTimeMinutes property in SampleTimeCounterStruct (which is a struct), the view updates as expected. However, when I update the showerTimeMinutes property in SampleTimeCounter (which is a class), the view does not update. However I have used the @Publshed property and it not updating the view as well.