is there anyway to achieve an

actual

value in an

expect class

which references a value not given yet? for example I want to achieve

val incoming: ReceiveChannel<Frame>
val incomingText: Flow<String> = incoming.consumeAsFlow().filter { it is Frame.Text }.map { (it as Frame.Text).payload }

where

incomingText

is basically a convenience method to give to consumers of that class. the error here states

Expected property cannot have an initializer

extension function is the way to go here afaik. expected declarations cannot have a body

alright well thats good enough for now then

The error seems to be about the initializer, so wouldn’t

get()

work here?

val incoming: ReceiveChannel<Frame>
val incomingText: Flow<String>
  get() = incoming.consumeAsFlow().filter { it is Frame.Text }.map { (it as Frame.Text).payload }

interesting let me try that

No it would not work, since this is also a declaration body

still getting an error there "Expected declaration must not have a body"

Fair enough then. If you have to declare an extension, you can also declare an extension property (not necessarily an extension function).

does this somehow relate to why so many ktor and some Flow functions are written as extensions functions?

I think the reason for that would mostly be because Kotlin designers thrive for extension-oriented design (especially in coroutines). But this is related: basically the principle is to declare the core of your interface as real properties/methods, and all the “convenience” stuff should only be extensions. Since the

expect/actual

mechanism is about implementing the core of the logic on each platform, it is sort of by definition that the rest (common code) is just “convenience”.

awesome an article from Roman. that makes sense, its interesting to see libraries be used like this more - seems like a step further into kotlin rather than improved java