Hey all, new to KMP and exploring the feasibility ...

# javascript

[Kalalau Cantrell]

Hey all, new to KMP and exploring the feasibility of creating a shared lib that can be used across iOS, Android, and web (TS + React).

My specific question is how are people working around the limitation where kotlin.collections.List can’t be exported with @JsExport?

With my limited experience in KMP, see below for something I’ve cobbled together that’s been working but it does not seem ideal. For instance, converting to and from List and having to create wrappers for every collection type takes away from the dream of writing business logic once at a high level and reusing it across platforms.

Does anyone have advice for doing this in perhaps a more generic way? Has anyone found a way to use expect / actual as a better solution?

@ExperimentalJsExport
@JsExport
class PeopleList : MutableList<StarWarsPerson> by mutableListOf() {
    fun toArray(): Array<StarWarsPerson> {
        val array = emptyArray<StarWarsPerson>()
        this.forEachIndexed { index, person ->
            array[index] = person
        }
        return array
    }

    companion object {
        fun fromArray(people: Array<StarWarsPerson>): PeopleList {
            val peopleList = PeopleList()
            peopleList.addAll(people)
            return peopleList
        }
    }
}

@ExperimentalJsExport
@JsExport
data class StarWarsPerson(val name: String

[Big Chungus]

Create your expect/actual list wrapper that is external interface on js and encapsulates array, while being regular interface encapsulating list on other platforms

[Big Chungus]

Then you can @JsExport js actual

[Big Chungus]

If you need to construct them from common,make some builder functions via expect actual too

[Kalalau Cantrell]

Thanks for the tips! I’ll give this a shot.

[grahamborland]

See also https://github.com/deezer/KustomExport as a possible alternative to @JsExport.

[Seth Madison]

FWW, we are shipping a JS/Android/Apple lib and ended up just using Array internally and externally.

The performance hit you take in JS for using a List is staggering.

We’re hoping to adopt https://github.com/JakeWharton/platform-collections when it is ready.