Hi guys, I wasn't sure if <#CR4P8KNKY|> is a good ...

# compose

[Stepan Revytskyi]

Hi guys, I wasn't sure if #CR4P8KNKY is a good place for that question, so I'm writing here.

I'm migrating to type-safe Compose navigation and encountered an issue with passing arguments to a nested navigation graph. I need to pass an argument uuid (for example) to the start destination of a nested graph.

I noticed that navigation() has a typeMap, like composable(), so I placed my argument there. However, I'm unsure how to retrieve the uuid in AuthScreens.SignIn.

Here’s an example version of my code:

@Serializable
@Parcelize
sealed class Screens : Parcelable {
    @Serializable data object Greeting : Screens()
    @Serializable data class Auth(val uuid: String) : Screens()
}

@Serializable
@Parcelize
sealed class AuthScreens : Parcelable {
    @Serializable data object SignIn: AuthScreens()
    @Serializable data object ResetPassword: AuthScreens()
}

@Composable
fun MyApp() {
    val navController = rememberNavController()
    NavHost(
        navController = navController,
        startDestination = Screens.Greeting,
        builder = {
            composable<Screens.Greeting> {
                // screen content 
                navController.navigate(Screens.Auth(uuid = "some_id"))
            }
            navigation<Screens.Auth>(
                startDestination = AuthScreens.SignIn,
                typeMap = mapOf(typeOf<String>() to NavType.StringType),
                builder = {
                    composable<AuthScreens.SignIn> {
                        // screen content
                        //TODO: how to get args ???
                    }
                    composable<AuthScreens.ResetPassword> {
                        // screen content
                    }
                }
            )
        }
    )
}

Could someone guide me on how to retrieve the uuid in AuthScreens.SignIn?

[ef]

> @Serializable
> @Parcelize
> sealed class AuthScreens : Parcelable {
> @Serializable data object SignIn: AuthScreens()
> @Serializable data object ResetPassword: AuthScreens()
> }
First of all, you would want to use a sealed interface to represent your screens as you will have trouble serializing generic classes


For retrieving data you can inside your navhost retrieve arguments from your backstackEntry. I’m guessing it will work something like this:

composable<AuthScreens.SignIn> {
                        // screen content
                        //TODO: how to get args ???
val route = it.savedStateHandle.toRoute<AuthScreens.SignIn>()

// you can now access properties of the route
                    }

[Stepan Revytskyi]

but AuthScreens.SignIn doesn't contains args, so .toRoute() will failed

[Stepan Revytskyi]

just realized that I can use a separate screen for the host NavHost and avoid using navigation() altogether

[Zach Klippenstein (he/him) [MOD]]

Please keep longer code snippets to the thread

[Stepan Revytskyi]

Sure 🤝