Unable to rerender a View using onAppear - swift

Question

I am trying to show a pause button if a sound file is playing, i have a uniform source of truth for the sound file, which i can access via ViewModel, now all works well on other Views, but on parent View where all navigation links are, when i go back to it using the back button from other Views, the miniplayer that shows pause disappears...
So i decided that on the .onAppear of NavigationView or text view of parent View i will implement the logic that can detect if a sound file is playing and if so , show a button at bottom to pause the sound file.
Now i can use print and it shows correct value on onAppear in terms of sound file playing or not, but the moment i try to use HStack or any other View to be added i get warning -
Result of 'HStack<Content>' initializer is unused
Now if i decide to use State then also i get similar warning, how can i make the View rerender onAppear, or is that not possible, if that is the case from where i can implement this logic, thanks ....
import Foundation
import SwiftUI
struct HomePageTabView: View {
#Binding var songLVM: SongListVM
#State var miniBar: Bool = false
init(songLVM: Binding<SongListVM>){
self._songLVM = songLVM
UITableView.appearance().backgroundColor = UIColor(.white)
}
var body: some View {
NavigationView {
List {
//Artists
NavigationLink(
destination: ArtistList(songLVM: $songLVM))
{
HStack {
Image(systemName: "music.mic")
Text("Artists")
}
}
//Albums
NavigationLink(
destination: Text("Albums"))
{
HStack {
Image(systemName: "music.note.list")
Text("Albums")
}
}
//Collections
NavigationLink(
//destination: ArtistView())
destination: ArtistViewMain( songLVM: $songLVM))
{
HStack {
Image(systemName: "music.quarternote.3")
Text("Collections")
}
}
//About Us
NavigationLink(
destination: Text("About Us"))
{
HStack {
Image(systemName: "music.note.house.fill")
Text("About Us")
}
}
//Contact Us
NavigationLink(
destination: ArtistView())
{
HStack {
Image(systemName: "phone.circle")
Text("Contact Us")
}
}
}
}
.onAppear {
if(songLVM.audioPlayer?.isPlaying != nil){
HStack {
Button("Stop") {
songLVM.audioPlayer?.stop()
}
}
}
}
}
}
I had also tried
.onAppear{
miniBar.toggle()
if(miniBar == true){
HStack {
Text("Stop")
}
}
}
but got Result of 'HStack<Content>' initializer is unused

Answer 1

I will give easy and basic template for working with swift's ui states.
You can refer it and add your views or navigation link.
struct YourView: View {
/// If you want to pass it on init, use #ObservedObject instead
/// https://www.hackingwithswift.com/quick-start/swiftui/whats-the-difference-between-observedobject-state-and-environmentobject
#StateObject var viewModel = YourViewModel()
var body: some View {
NavigationView {
VStack {
if viewModel.isPlaying {
Button {
viewModel.stop()
} label: {
Text("Stop")
}
} else {
Button {
viewModel.start()
} label: {
Text("Start")
}
}
Toggle(isOn: $viewModel.isPlaying) {
Text("isPlaying")
}
}
}
.onAppear {
viewModel.transform()
}
}
}
class YourViewModel: ObservableObject {
#Published var isPlaying = false
func transform() {
fetchStatus()
}
func fetchStatus() {
isPlaying = true
}
func stop() { isPlaying = false }
func start() { isPlaying = true }
}