What is the ideal way to deal with arguments for a...

# compose-android

[Ahmed]

What is the ideal way to deal with arguments for a navigation graph? 🧵

[Ahmed]

I have a NavHost setup as

NavHost(
    navController = navController,
    startDestination = BaseRouteGraphA,
    modifier = Modifier.fillMaxSize(),
) {

    graphA(
        navController = navController,
        onSomeThingSelected = { 
            navController.navigateToGraphB(it.myIdThatINeed)
        }
    )

    graphB( … )
    graphC( … )

}

And within graph B

I am currently obtaining the data I need by

fun NavController.navigateToGraphB(myIdThatINeed: Int) {
    navigate(route = BaseRouteGraphB(myIdThatINeed))
}

fun NavGraphBuilder.graphB( … ) {
    navigation<BaseRouteGraphB>(startDestination = ScreenB1) {
        composable<ScreenB1> { backStackEntry ->
            backStackEntry.arguments.getInt("myIdThatINeed")
            …
        }

        composable<ScreenB2> { … }
        composable<ScreenB3> { … }
    }
}

[Ahmed]

I was wondering if this approach is correct? Or if there is a better way to handle this

[Stylianos Gakis]

Yeah, using the type-safe navigation APIs, you should use this https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:navigation/navigation-common/src/main/java/androidx/navigation/NavBackStackEntry.kt;l=300?q=toRoute instead.
It's a one liner and you get back the entire destination object. From there you can use the arguments in any way you wish, it's super simple.

[Ahmed]

I require the argument in ScreenB1 . But if you notice, the argument was passed to the BaseRouteGraphB

[Stylianos Gakis]

Here's it in action.
https://github.com/HedvigInsurance/android/blob/develop/app%2Fnavigation%2Fnavigation-compose%2Fsrc%2Fmain%2Fkotlin%2Fcom%2Fhedvig%2Fandroid%2Fnavigation%2Fcompose%2FNavGraphBuilderExt.kt#L55

[Stylianos Gakis]

Yeah you can grab the NavBackstackEntry of your graph to do the .toRoute on.

[Stylianos Gakis]

navController.getBackStackEntry<BaseRouteGraphB>()

[Ahmed]

Thanks, this indeed works.

navController.getBackStackEntry<BaseRouteGraphB>().toRoute<BaseRouteGraphB>()