StateVsObserved

import SwiftUI

final class MyViewModel: ObservableObject {
    @Published var counter: Int = 0
}

struct MainView: View {
    @StateObject var myViewModel = MyViewModel()
    var body: some View {
        VStack {
            VStack(spacing: 0) {
                Group {
                    Text("\(myViewModel.counter)")
                        .font(.largeTitle)
                }
                .padding()
                .background { Color.white }

                Button {
                    myViewModel.counter += 1
                } label: {
                    Text("Increment counter")
                        .padding()
                        .background { Color.white }
                        .clipShape(Capsule())
                }
                .padding(8)

            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
            ChildView()

        }

    }
}

struct ChildView: View {
    // Changing it to @StateObject will keep the object value
    @ObservedObject var viewModel: MyViewModel = MyViewModel()
    var body: some View {
        VStack {
            Text("I'm the child: \(viewModel.counter)")
                .padding(50)
                .font(.largeTitle)
                .background {
                    Color.random()
                }
            Button {
                viewModel.counter += 1
            } label: {
                Text("Increment counter in child")
                    .padding()
                    .foregroundStyle(.white)
                    .background { Color.red }
                    .clipShape(Capsule())
            }
        }
    }
}

#Preview {
    MainView()
}

extension Color {
    static func random() -> Color {
        return Color(
            red: Double.random(in: 0...1),
            green: Double.random(in: 0...1),
            blue: Double.random(in: 0...1)
        ).opacity(0.5)
    }
}