How can I block while a coroutine is running? My use case is that I'm confining operations to one th...

# coroutines

[addamsson]

How can I block while a coroutine is running? My use case is that I'm confining operations to one thread in a class which has shared mutable state so I have to use a single threaded coroutine dispatcher, but I also want to provide a synchronous interface for my users. How can I do this?

[Jacques Smuts]

you can run all the suspend functions through a Mutex() that only allows one suspend function at a time 🤔. But not sure if that would be the ideal solution for your usecase.

[addamsson]

no it is not, i tried that but it is extremely slow

[addamsson]

my current setup is fine

[addamsson]

in regards to speed

[addamsson]

i have presistent data structures so reads are not confined (no coroutines)

[addamsson]

writes are confined, but I only want to return from a mutating method when the mutation is complete

[Jacques Smuts]

so you have

suspend fun doWrite(input): Result {}

and

fun doWriteSync(input): Result {
    scope.launch{ doWrite(input) }
}

And the suspend function works fine and returns when it returns, but you want the synchronous blocking one to return only when the suspend one is done?

[addamsson]

yes

[gildor]

scope.launch -> runBlocking?

[addamsson]

i don't have access to runBlocking

[addamsson]

i'm not sure how can I use that

[addamsson]

no code completion

[ahulyk]

try GlobalScope.runBlocking {}

[gildor]

is this MPP project?

[gildor]

runBlocking available only on JVM and Native, but not on JS (because there is just no proper way to block thread), so it’s not available there

[Dominaezzz]

If you don't have a JS target, you can do expect/actual for runBlocking.

[addamsson]

this is MPP, yes

[addamsson]

so I have a workaround now

[addamsson]

I refactored my methods which use coroutines to not return a value

[addamsson]

and I have getters which aren't using coroutines but safe to call, because they are using persistent data structures

[addamsson]

do any of you have a better idea for this?

[Pablichjenkov]

If I understand correctly, you want to execute a sequence of write operations on some mutable shared state.
Have you tried the Channel api. It behaves as a blockingQueue basically, where you can send message/operations in a queue manner.

[addamsson]

no, as it turns out what I need is @Synchronized 😄