Hey, I am currently migrating to the latest versio...

# javascript

[Hildebrandt Tobias]

Hey, I am currently migrating to the latest version (from v2025.7.15).
I am a little confused how the new data loaders work. Before I had it like this for example:

val VehicleClassLoader = LoaderFunction<Array<VehicleClassDto>?> { args, _ ->
    val vehicleClassId = args.params["id"]
    if (vehicleClassId == "-1") return@LoaderFunction PromiseResult(null)
    val endpoint = VehicleClassEndpoints.getVehicleClass.copy(
        optionalQueryParams = pairListOf("id" to vehicleClassId.toString())
    )
    val vehicleClass = secureApi(endpoint)
    PromiseResult(vehicleClass)
}

[Edoardo Luppi]

I suppose this is related to kotlin-wrappers right?

That declaration seems to come from the legacy router types that were removed in favor of TanStack Router.

[Hildebrandt Tobias]

Yes I am trying to migrate it to the latest version, this example is from the legacies before.
It seems I have followed the wrong path down the types, before it was something like () -> Unit.
But now I found RouteLoaderFn that provides options and expects a PromiseResult.

Seems like this is correct(?) for now

val VehicleClassLoader = RouteLoaderFn { options ->
    val vehicleClassId = options.params[ParamName("id")]
    if (vehicleClassId == "-1") return@RouteLoaderFn PromiseResult(null)
    val endpoint = VehicleClassEndpoints.getVehicleClass.copy(
        optionalQueryParams = pairListOf("id" to vehicleClassId.toString())
    )
    val vehicleClass = secureApi(endpoint)
    PromiseResult(vehicleClass)
}

Sorry for the trouble but the other type chain really confused me.

[Edoardo Luppi]

@turansky probably Victor knows how to translate that as my React knowledge is very limited.

[turansky]

RouteLoaderFn wrapper will do required work (it will create promise).
PromiseResult call is redundant.

[turansky]

Just return secureApi(endpoint)

[turansky]

Or null

[Hildebrandt Tobias]

Oh, thanks! Sorry for the interruption ❤️

[turansky]

Our goal - Kotlinish API.
And we create wrappers like this for your comfort.

[turansky]

If in some case it doesn't look cool - please report.

[Hildebrandt Tobias]

Yeah that's the one I found after searching some more.
Don't know where the follow reference function from IDEA put me to find the other stuff.
This makes way more sense.

[turansky]

Looks like you saw private signature 😞