I have a question, I’m trying to replace promises with coroutines but I can’t figure out a way to cr...

# coroutines

[Brian Estrada]

I have a question, I’m trying to replace promises with coroutines but I can’t figure out a way to create a Deferred<Int> and then call it and complete it later by another function (Will add an example in a 🧵)

[Brian Estrada]

fun main(args: Array<String>) {
    val hashMap = HashMap<String, Deferred<Int>>()

    GlobalScope.launch {
        delay(2000)
        println("done waiting")
        requireNotNull(hashMap["test"]).asCompletableFuture().complete(5)
    }

    runBlocking {
        val asyncThing = async {
            getNumberFive()
        }

        hashMap["test"] = asyncThing

        println(asyncThing.await())
    }
}

[Brian Estrada]

I guess basically what I want to do is be able to create deferrable and complete it later in another part of the code, is this a bad use case of coroutines and should I just keep using promises? 🤔

[stojan]

You are looking for CompletableDeffered

https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-completable-deferred/

[Brian Estrada]

@stojan thank you!!

[streetsofboston]

What about starting async lazily?
var asyncThing = async(start=CoroutineStart.LAZY) { ... }