Hi there,

Im currently creating an app for an index of sheet music and I wish to filter the songs via favourites. I have the code down and am using ObservableObject data store to change the bool but when I change the toggle button in a detail view the change does not carry over in the list. the list does not automatically change. I beleive its because I'm using ObservedObject rather that EnvironmentalObject. I Thought to use this you need to change SceneDelegate but I created the app in Xcode 12 and there is no SceneDelegate. The toggle changes the isFavourite but doesnt update the list.

see code below:

import Combine
import SwiftUI

final class UserData: NSObject, ObservableObject {
    @Published var showFavoritesOnly = false
    @Published var songs = songData
}

struct ListView: View {

    @ObservedObject var userData = UserData()

    var body: some View {
        NavigationView {
            List {
                ForEach(userData.songs, id: \.id) { song in
                    if !self.userData.showFavoritesOnly || song.isFavorite {
                        NavigationLink(destination: DetailView(data: song)) {
                            RowView(data: song)
                        }
                    }
                }
            }
            .navigationBarTitle("Music Index", displayMode: .inline)
            .navigationBarItems(trailing:
                                    Toggle(isOn: $userData.showFavoritesOnly) {
                                        Image(systemName: "circle.fill")
                                            .foregroundColor(.blue)
                                    })
        }
    }
}

struct DetailView: View {

    var data: DataSection

    @ObservedObject var userData = UserData()

    var songIndex: Int {
        userData.songs.firstIndex(where: { $0.id == data.id })!
    }

        var body: some View {
            ZStack {
                Color(.white)
                VStack {
                    Button(action: {
                        self.userData.songs[self.songIndex]
                            .isFavorite.toggle()
                    }) {
                        Text("Select as favourite")
                            .fontWeight(.heavy)
                            .foregroundColor(.black)
                        if self.userData.songs[self.songIndex]
                            .isFavorite {
                            Image(systemName: "circle.fill")
                                .foregroundColor(Color.blue)
                        } else {
                            Image(systemName: "circle")
                                .foregroundColor(Color.blue)
                        }
                    }.padding(.top)

                    Image(data.songNumber)
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                        .onAppear { UIApplication.shared.isIdleTimerDisabled = true }
                        .onDisappear { UIApplication.shared.isIdleTimerDisabled = false }
                    Spacer()
                }
            }
        }
    }

Thankyou so much!

I have read and am keeping the page bookmarked for future reference. Im learning everyday with swift development and having people like you that explain it so well and am patient with me as a noob lol. I entered a @StateObject in the main struct and then used the environment modifier.

@main
struct Song_IndexApp: App {

    @StateObject var music = UserData()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(music)
        }
    }
}