Hilt and ViewModel initialization with Navigation Component arguments

[langsmith]

Hilt and ViewModel initialization with Navigation Component arguments

[langsmith]

I'm looking into https://airbnb.io/mavericks/#/fragment-arguments?id=using-fragment-args-in-the-initial-value-for-mavericksstate

The following might work:

LoginFragmentDirections.actionLoginFragmentToHome(userFullName = it.userFullName)

data class HomeState(
    val userFullName: String,
    val paymentList: Async<List<Payment>> = Uninitialized,
    val coarseLocationPermissionGranted: Boolean = false,
    val deviceLastLocationCoordinates: Pair<Double, Double> = Pair(0.0, 0.0),
    val count: Int = 0
) : MavericksState {

constructor(homeFragmentArgs: HomeFragmentArgs) : this(userFullName = homeFragmentArgs.userFullName.orEmpty())

[langsmith]

I'm looking into https://airbnb.io/mavericks/#/fragment-arguments?id=using-fragment-args-in-the-initial-value-for-mavericksstate

The following might work:

LoginFragmentDirections.actionLoginFragmentToHome(userFullName = it.userFullName)

data class HomeState(
    val userFullName: String,
    val paymentList: Async<List<Payment>> = Uninitialized,
    val coarseLocationPermissionGranted: Boolean = false,
    val deviceLastLocationCoordinates: Pair<Double, Double> = Pair(0.0, 0.0),
    val count: Int = 0
) : MavericksState {

constructor(homeFragmentArgs: HomeFragmentArgs) : this(userFullName = homeFragmentArgs.userFullName.orEmpty())

Nah, that alternate constructor setup didn't work. Not sure whether or not it's because I'm not doing the steps 👇🏽

[langsmith]

Well things ARE working when I follow the steps above

1. 
2. 
3. 

However, this process seems opposite to using the arguments declared in the Navigation Component nav graph XML file. I still have to create custom Parcelizable argument data classes 😕 I'm unable to use generated _____Directions and do something like

findNavController().navigate(LoginFragmentDirections.actionLoginFragmentToHome(userFullName = it.userFullName))

I know that custom Parcelable objects can be passed through as arguments

---

However, this doesn't really help me from avoiding having to create these custom args classes in the first place 😕

[langsmith]

Any thoughts on this @gpeal @elihart ?

[langsmith]

Doesn't really address this ticket's topic/question, but another option I just thought of was to save the full name to repo-level persistence in LoginViewModel and just fetch it in HomeViewModel instead of passing it at Navigation Component arguments from one fragment/VM to another.

[langsmith]

Closing the loop here. This is what I've ultimately ended up with and I'm posting it here mainly so that others might benefit from it.

I created a setAsMavericksArgs extension function, which has made things pretty easy and minimal when going from one fragment/VM to another.

import android.os.Parcelable
import kotlinx.parcelize.Parcelize

@Parcelize
class ParcelableClassWithArgs(
    var stringValue: String? = "",
    var booleanValue: Boolean? = false,
): Parcelable

Parcelable extension function 👇🏽

fun Parcelable.setAsMavericksArgs(fragment: Fragment): Bundle {
    this.asMavericksArgs().let {
        fragment.arguments = it
        return it
    }
}

Fragment extension function 👇🏽

fun Fragment.navigate(actionInt: Int, optionalArgs: Bundle? = null) =
    findNavController().navigate(actionInt, optionalArgs)

Navigating in the Fragment 👇🏽

navigate(
    NavGraphDirections.actionToNextFragment().actionId,
    ParcelableClassWithArgs(
		...various values
	).setAsMavericksArgs(this)
)

Setup in the ViewModel of the Fragment that has been navigated to

data class ReceivingViewModelState(
    val args: ParcelableClassWithArgs? = null,
) : MavericksState {
    constructor(parcelableClassWithArgs: ParcelableClassWithArgs) : this(args = parcelableClassWithArgs)
}