Hello, newbie to native world. What is the best way to handle obj c functions that throws an excepti...

# kotlin-native

[ayodele]

Hello, newbie to native world.
What is the best way to handle obj c functions that throws an exception. Basically they carry an extra param with a type CPointer<ObjCObjectVar>NSError?>>.
Using try and catch is not useful and I don't want to pass in null

[Sam]

I have this little utility function I use

import kotlinx.cinterop.CPointer
import kotlinx.cinterop.ObjCObjectVar
import kotlinx.cinterop.alloc
import kotlinx.cinterop.memScoped
import kotlinx.cinterop.ptr
import kotlinx.cinterop.value
import platform.Foundation.NSError

class NSErrorException(val nsError: NSError) : Exception(nsError.localizedDescription)

inline fun <T> throwNSErrors(block: (CPointer<ObjCObjectVar<NSError?>>) -> T): T = memScoped {
    val err = alloc<ObjCObjectVar<NSError?>>()
    val result = block(err.ptr)
    if (err.value != null) throw NSErrorException(err.value!!)
    result
}

[ayodele]

Thank you @Sam

[ayodele]

@Sam do you know how to observe properties from Kotlin?? Like we can do from Swift with addObserver

[Sam]

Hmm... I'd need to see an example. I don't think I've ever used addObserver in Swift.

[Sam]

It is worth noting that Kotlin uses Objective-C as a go-between with Swift. So some Swift-only APIs/idioms aren't directly available to Kotlin.