API design question which would you use to pass around a read only value that gets initialized once and cached 1 `suspend gt T` 2 `Deferred lt T gt ` Vote one for `suspend fun gt T` or two for `Deferred lt T gt `

you d still return `Deferred lt T gt ` but internally you would hand off the value to create a gap

API design question which would you use to pass around a rea kotlinlang #coroutines

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zak.taccardi

07/29/2019, 6:42 PM

API design question - which would you use to pass around a read-only value that gets initialized once and cached? 1.

suspend () -> T

Deferred<T>

Vote 1️⃣ for

suspend fun () -> T

or 2️⃣ for

Deferred<T>

1️⃣ 7

2️⃣ 4

I see

suspend () -> T

as a more abstract approach, but it requires more boilerplate + some extra anonymous classes

Deferred<T>

has a lot less boilerplate to implement, more clearly indicates that the value will be cached, but it exposes its underlying

Job

API, which a caller could accidentally cancel

octylFractal

07/29/2019, 6:45 PM

if you're worried about the cancellation, just create a separate

CompletableDeferred

that's not part of the job.

zak.taccardi

07/29/2019, 6:46 PM

CompletableDeferred

extends

Deferred

so it’s worse. This isn’t an API that you would want to allow callers to be able to complete. It’s read only

octylFractal

07/29/2019, 6:46 PM

I don't mean return it -- I mean use it to prevent cancellation of the underlying job

you'd still return

Deferred<T>

, but internally you would hand-off the value to create a gap

zak.taccardi

07/29/2019, 6:47 PM

oh, very interesting

Dominaezzz

07/29/2019, 7:36 PM

Interface version of option 1 I think.

zak.taccardi

07/30/2019, 12:25 AM

I’m not a fan of the interface approach as that is less flexible

louiscad

07/30/2019, 2:59 PM

I'm using top level functions to initialize top level `val`s of the

SuspendLazy

type: https://github.com/LouisCAD/Splitties/blob/develop/modules/coroutines/src/commonMain/kotlin/splitties/coroutines/SuspendLazy.kt https://github.com/LouisCAD/Splitties/blob/develop/modules/coroutines/src/jvmMain/kotlin/splitties/coroutines/SuspendLazyJVM.kt

zak.taccardi

07/30/2019, 3:00 PM

interesting idea, but I would like to avoid introducing a custom type

louiscad

07/30/2019, 10:58 PM

Well, you can make the top level

val

private, and make a top level suspending function getting the value from it.

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