Hi, My Android app uses Ktor for network requests,...

# android-architecture

[KotlinLeaner]

Hi, My Android app uses Ktor for network requests, and I have a separate module for handling API calls. I've implemented 401 error handling to trigger a logout. However, my navigation logic, including the NavHost, is in the app module. What's the best way to signal the NavHost to perform the logout action when a 401 error occurs?

[marlonlom]

Do you use Result<T> (https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-result/) as the http api response? the 401 error can be converted to a Result.failure and returned to the navhost using the ui state you've defined

[Vivek Modi]

do you have any example?

[eyedol]

Without knowing much about your code base. In your ViewModel or where ever you're calling a function to make a network call that will cause the 401, you could catch the exception that would be thrown and then check to make sure it's an exception due to a 401 then react to it by sending an event or UI state to the UI to cause a logout or directly logout from there – where you are catching the 401 error. See this sample implementation in the Tivi app for an example: https://github.com/chrisbanes/tivi/blob/main/ui/root/src/commonMain/kotlin/app/tivi/home/RootViewModel.kt#L50

[KotlinLeaner]

Thank you so much. I'll take a look on that.

[Ahmet Özcan]

You can keep a singleton state flow named like "AuthenticationStatus" and have a sealed class like
object NotAuthenticated: AuthenticationStatus
data class Authenticated(val user: User): AuthenticationStatus
object SignedOut: AuthenticationStatus
....
Then listen this flow in some top level viewmodel has access to a navigation manager and you can emit state from api level