Anyone know current state of using lambas with a return value of Unit in native? Currently in swift I have to always return a KotlinUnit() from a lambda. I've seen an open issue. Has this changed, or will this change in future versions of KN? i.e. to pass a lamda to a Kotlin function we must do:

myKtFun { dostuff()
    return KotlinUnit() }

If you enable the generics then the return type changes to Void. So you don’t need to add a return statement anymore.

I'm using 1.3.41 with generics and still have to use return statements. I suppose that is in a newer release

I am using 1.3.41 as well and don’t have to add the return to lamdas. Are you sure the generics are enabled correctly using

-Xobjc-generics

?

I also didn’t not have to return KotlinUnit() anymore with 1.3.41. `-Xobjc-generics`wasn’t enabled in my case.

Kotlin 1.3.40 has the following in the release notes:

In addition to this, the Kotlin type Unit will turn into Void in the produced frameworks.

It was just below the generics supports so I thought you needed the generics for this. But it looks like it works without the generics as well.

It is working on 1.3.41 for me now that I go back and clean & rebuild. Thanks Thomas

I was pretty surprised by the generics part and was going to comment, but got distracted …

@kpgalligan yes, sorry about that. I don't think it is really clear in the 1.3.40 change log if this was in addition to generics or to the whole update. It says "in addition to this..". I thought it referred to the generics part.

Yeah, I can see that getting confused. I was surprised when we updated to 1.3.4x that Unit went away. It’s pretty nice not having to do that.

They improved it in many cases in 1.3.41. If you found a case they missed, you should file a GH issue

Generics are irrelevant here.

The docs still say you need to add the return. I guess this still needs to be updated?

Yes, thanks.

myKtFun { dostuff()

return KotlinUnit() }

myKtFun

is likely not a function but a function-typed object here.

Unit

is not represented as

Void

when in is that deep. I.e.

() -> Unit

type becomes

() -> Void

, but

(() -> Unit) -> Unit

becomes

(() -> Unit) -> Void

.

@svyatoslav.scherbina Ok, yes I still have to

return KotlinUnit()

in some situations. My usecase is a

typealias Subscriber = () -> Unit
fun subscribe(subscriber: Subscriber) { ... }

Think this will ever go away? or is there some limitation that is blocking

Then you either use older version of Kotlin or the usecase is more complex. This

subscribe

case works properly for me. Could you recheck?

I see now, yes it is more complex.

typealias Subscription = () -> Unit
val subscribe: (Subscriber) -> Subscription

using

subscribe  { }

from swift forces me to

return KotlinUnit()

Then how is it different from what i’ve described above? https://kotlinlang.slack.com/archives/C3PQML5NU/p1565681457378500?thread_ts=1565633800.374800&cid=C3PQML5NU

yes, see that sorry...just asking if you think this will likely change in a future version of kotlin. If you think the more complex function-typed objects (such as (

() -> Unit) -> Unit)

ever be able to return Void from Swift. Bit of a pain point when using from swift.

We have no ETA for this.