Hi Foks, I’m getting `kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of froze...

# multiplatform

[sushma nayak]

Hi Foks,
I’m getting kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen exception.

Dependencies info -
kotlin = "1.4.30"
coroutines = "1.4.2-native-mt"
serialization = "1.0.1"
ktor = "1.4.2"

This is what I’m doing -

class Manager {
 var user: User
 init(){
  GlobalScope.async(context = Dispatchers.Default) {
  val result = callToSuspendFunction
  user = result //ERROR ON THIS LINE
 }
}

How to achieve something like this?

[uli]

You can not. You can't access a mutable variable (user) from two threads. Here user was probably created on the main thread and is written from default dispatcher.

[sushma nayak]

Thanks for your quick response @uli.
Yes, I’m calling this init from main thread.

[Vitor Prado]

i think you can assign value using MainScope or using the Dispatchers.Main

[KamilH]

You can use AtomicReference. In your case it would simply be:

val user: AtomicReference<User?> = AtomicReference(null)

If you’re writing a multiplatform code you could be interested in on of those two libraries:
https://github.com/Kotlin/kotlinx.atomicfu
https://github.com/touchlab/Stately

You can read more about why it’s needed here:
https://kotlinlang.org/docs/mobile/concurrent-mutability.html