class AuthState: ObservableObject {
   init() {}
}

struct ContentView: View {
    var body: some View {
        RootView()
            .environmentObject(AuthState())
    }
}

struct RootView: View {
    @EnvironmentObject var authState: AuthState // 💡 Obtained via `@EnvironmentObject`.
    @ObservedObject var viewModel: RootViewModel
    
    init() {
        // 🚫 Compile error: 'self' used before all stored properties are initialized.
        viewModel = RootViewModel(authState: authState)
    }
    
    var body: some View { ... }
}
    
class RootViewModel: ObservableObject {
    private let authState: AuthState // 💡 RootViewModel required `AuthState`.
    
    init(authState: AuthState) {
        self.authState = authState
    }
}

struct RootView: View {
    @EnvironmentObject var authState: AuthState

    // 🚫 Compile error:
    // Cannot use instance member 'authState' within property initializer; 
    // property initializers run before 'self' is available
    @ObservedObject var viewModel = RootViewModel(authState: authState)
    
    var body: some View { ... }
}

struct RootView: View {
    @EnvironmentObject var authState: AuthState

    // 🚫 Compile error: Property 'viewModel' with a wrapper cannot also be lazy
    @ObservedObject lazy var viewModel = RootViewModel(authState: authState) // 💡 Try `lazy` keyword.
    
    var body: some View {}
}

struct RootView: View {
    @EnvironmentObject var authState: AuthState
    @ObservedObject var viewModel = RootViewModel()
    
    var body: some View {
        Text("Hello")
            .onAppear {
                viewModel.inject(authState) // 🚫 Should definitely avoided!!
            }
    }
}

class RootViewModel: ObservableObject {
    private var authState: AuthState!
    
    // 💡 DI by method injection.
    func inject(_ authState: AuthState) {
        self.authState = authState
    }
}

struct RootView: View {
    @EnvironmentObject var authState: AuthState
    @StateObject var viewModel = RootViewModel() // ✅ Use `@StateObject`
    
    var body: some View {
        Text("Hello")
            .onAppear {
                viewModel.inject(authState)
                viewModel.onAppear()
            }
    }
}

class RootViewModel: ObservableObject {
    private var authState: AuthState!
    
    func inject(_ authState: AuthState) {
        self.authState = authState
    }
    
    func onAppear() {
        // 💡 Use `authState`
    }
}