Source: https://developer.apple.com/documentation/swiftui/managing-user-interface-state

This example shows how @State is used.

struct PlayerView: View {
    @State private var isPlaying: Bool = false

    var body: some View {
        Button(action: {
            self.isPlaying.toggle()
        }) {
            Image(systemName: isPlaying ? "pause.circle" : "play.circle")
        }
    }

}

You need to put the view as root view and run the APP

let contentView = PlayerView().environment(\.managedObjectContext, context)