Hi, i’m using kotlin-multiplatform plugin to creat...

# kotlin-native

[Andrei Marshalov]

Hi, i’m using kotlin-multiplatform plugin to create ios framework and android aar library.
Since i use interop with c-libraries in my project i need to do some special stuff at the end of using my objects: call function, that will free memory, allocated by c-functions.
To be sure that memory is always freed (eg if an exception is thrown) i added my own Closeable interface and copied use extension from <http://kotlin.io|kotlin.io> package. It looks like:

interface Closeable {

    fun close()
}

@Throws(Throwable::class)
inline fun <T : Closeable?, R> T.use(block: (T) -> R): R {
    var exception: Throwable? = null
    try {
        return block(this)
    } catch (e: Throwable) {
        exception = e
        throw e
    } finally {
        when {
            this == null -> {}
            exception == null -> close()
            else ->
                try {
                    close()
                } catch (closeException: Throwable) {
                    // cause.addSuppressed(closeException) // ignored here
                }
        }
    }
}

It works fine for android, but in Swift i have some problem. Function signature from xCode:

UtilitiesKt.use(receiver: Closeable?, block: (Closeable?) -> Any?, result: AutoreleasingUnsafeMutablePointer<AnyObject??)

use function in xCode marked as trowable, due to @Throws(Throwable::class) annotation, but if i try use trowable functions in block lambda, xCode says: Invalid conversion from throwing function of type '(Closeable?) throws -> Any?' to non-throwing function type '(Closeable?) -> Any?'

Maybe someone know, how can i mark lambda parameter as throwable in kotlin?

[Artyom Degtyarev [JB]]

Hello! This approach is unavailable for now. You can use an interface with a @Throws-annotated function instead of the lambda.

[Andrei Marshalov]

Thank you, will think about it. Are there any plans to add such approach?

[Artyom Degtyarev [JB]]

Sorry for a long silence. Unfortunately, it is not among the upcoming features. But as far as I know, there are some ideas on implementation.

[Andrei Marshalov]

Thank you for reply!