Suppose I have a suspend function that provides an instance of some interface. How can I use Koin to...

# koin

[Mark]

Suppose I have a suspend function that provides an instance of some interface. How can I use Koin to inject such an instance where required? Like mentioned https://github.com/InsertKoinIO/koin/issues/388

[Mark]

I’m thinking maybe the best way to go is for the instance to internally lazily perform some suspending init() rather than requiring the caller to explicitly do so.

[arnaud.giuliani]

can you be more explicit? 🤔

[Mark]

Suppose I have a singleton that requires a one time call to a suspending function init() before it can be used. Ideally any code that wants to use this singleton would call some suspending equivalent of get() (or somehow by inject()) in such a way that init() is called behind the scenes (presumably in some equivalent to single {} that takes a suspending lambda) only when necessary.

[Mark]

Currently, I do something like this:

single(named("instanceProvider")) {
    suspendableLazy {
        createAndInitInstance()
    }
}

and then:

private val instanceProvider by lazy {
   get<SuspendableProvider<MyClass>>(named("instanceProvider"))
}

suspend fun getInstance(): MyClass? = try {
    instanceProvider.get()
} catch (e: Exception) {
    Log.e("di", "unable to create instance", e)
    null
}

where using some common code:

interface SuspendableProvider<T> {
    suspend fun get(): T
    val isCompleted: Boolean
}

fun <T> suspendableLazy(provider: suspend () -> T) = object : SuspendableProvider<T> {
    private val computed = GlobalScope.async(start = CoroutineStart.LAZY) { provider() }

    override val isCompleted: Boolean
        get() = computed.isCompleted

    override suspend fun get() = computed.await()
}

[arnaud.giuliani]

yeah, can be interesting to something in this way yes 👍