//
//  MyApp.swift
//

import SwiftUI

@main
struct MyApp: App {

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

struct ContentView: View {

    @AppStorage("redBackground") private var redBackground: Bool = false

    var body: some View {
        ZStack {
            // Flipping "redBackground" will cause a reconstruction of the view hierarchy
            if redBackground {
                Color.red
            } else {
                Color.green
            }
            MyView(viewModel: MyViewModel())
        }
    }
}

final class MyViewModel: ObservableObject {

    init() {
        print("MyViewModel.init")
    }
}

struct MyView: View {

    @StateObject var viewModel: MyViewModel

    @AppStorage("redBackground") private var redBackground: Bool = false

    // WARNING: Uncommenting this causes the view model to be recreated every reconstruction of the view!
    //    init(viewModel: MyViewModel) {
    //        self._viewModel = StateObject(wrappedValue: viewModel)
    //    }

    var body: some View {
        VStack {
            Button("Toggle background") {
                redBackground = !redBackground
            }
        }
    }
}