Login form demonstrating change of focus using a view model

LoginVM.swift

class LoginViewModel: ObservableObject {
    @Published var username = ""
    @Published var password = ""
    @Published var focusedField: Field?
    
    enum Field: Hashable {
        case username
        case password
    }
    
    func signInButtonTapped() {  // async {
        if username.isEmpty {
            focusedField = .username
        } else if password.isEmpty {
            focusedField = .password
        } else {
            self.focusedField = nil
            // handle login
        }
    }
}


struct LoginForm: View {
    @StateObject var viewModel = LoginViewModel()
    @FocusState private var focusedField: LoginViewModel.Field?
    
    var body: some View {
        Form {
            TextField("Username", text: $viewModel.username)
                .focused($focusedField, equals: .username)
            
            SecureField("Password", text: $viewModel.password)
                .focused($focusedField, equals: .password)
            
            Button("Sign In") {
                viewModel.signInButtonTapped()
            }
        }
        .sync($viewModel.focusedField, $focusedField )
    }
}