I'm trying to use Ktor on iOS through a Kotin Mult...

# ktor

[gonzooin]

I'm trying to use Ktor on iOS through a Kotin Multiplatform project.

But I keep getting kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen error when i'm using on iOS ( the android part work well BTW )

I've defined a specific dispatcher for iOS like this :

internal val ApplicationDispatcher: CoroutineDispatcher = NsQueueDispatcher(dispatch_get_main_queue())

internal class NsQueueDispatcher(
    private val dispatchQueue: dispatch_queue_t
) : CoroutineDispatcher() {
    override fun dispatch(context: CoroutineContext, block: Runnable) {
        dispatch_async(dispatchQueue) {
            block.run()
        }
    }
}

And I use like this in a presenter that I will connect to the iOS UIViewController

class ExampleViewPresenter : BasePresenter() {

   fun test() {
        launch {
            try {
                val example =  ExampleSuspendMethod() 

                withContext(Main) {
                    println(example)
                }

            } catch (e: Throwable) {
                println(e)
            }
        }
}

I've defined the scope of launch in BasePresenter like this:

abstract class BasePresenter : CoroutineScope {

    private var job = Job()

    override val coroutineContext: CoroutineContext
        get() = ApplicationDispatcher + job

    fun onDestroy() {
        job.cancel()
    }

}

I've found people with the same error on stack overflow and on this channel but the cause was a bug in Kotlin 1.3.11 and I'm using 1.3.21.
I've found one similar project with the same version of Kotlin but I didn't succeed to make it work ( https://github.com/watabee/RakutenRankingKotlin )

Did anyone succeed to use Ktor client on iOS with Kotlin 1.3.21 ?

[e5l]

Please note that coroutines is not supported between multiple threads. What is Main dispatcher in your code?

[e5l]

Here you could find the working sample with ktor iOS client: https://github.com/JetBrains/kotlinconf-app

[gonzooin]

Thanks ! I will take a look to the example.
Main is not useful, old test code…

[Ellen Shapiro]

I’m having a similar issue. I’ve basically tried to get as much as I can from the KotlinConf app as I can but I’ve hit a brick wall.

My code is open source so you can poke it with a stick if you want: https://github.com/bakkenbaeck/porchpirateprotector

[Ellen Shapiro]

it seems to be actually hitting it in the post request - I tried pulling out the HttpRequestBuilder to a var instead of using a lambda, and it managed to get to the actual request before dying

[Ellen Shapiro]

I changed here: https://github.com/bakkenbaeck/PorchPirateProtector/blob/master/code/PPPShared/src/commonMain/kotlin/api/NetworkClient.kt#L67

[Ellen Shapiro]

to

val fullPath = fullURLStringForPath(path)
        var builder = HttpRequestBuilder()
        builder.url(fullPath)
        builder.body = data
        headers.forEach { builder.header(it.key, it.value) }
        println("POSTUN $data")

        return <http://ktorClient.post|ktorClient.post>(builder)

[Ellen Shapiro]

still hitting that println before it throws the exception

[Ellen Shapiro]

OK, maybe I found something? Diving through code from <http://HttpClient.post|HttpClient.post> down to HttpClient.request(Builder) to call.builder, I found this in io.ktor.client.call - the comments certainly say it mutates.

[Ellen Shapiro]

oops sorry, this is called from io.ktor.client.call.utils.kt - it’s in io.ktor.client.request.HttpRequest.kt

[Ellen Shapiro]

Pretty much everything from the convenience post / get etc methods goes through this which calls that:

[gonzooin]

Is your HttpClient a property of a singleton (object) ?

[Ellen Shapiro]

@gonzooin yes, it is!

[Ellen Shapiro]

have you found that to be an issue?

[ribesg]

We’re experimenting right now, but it may be the cause

[Ellen Shapiro]

interesting! I’ll poke at that and see what i come up with

[ribesg]

Yeah this was the issue. It still doesn’t work but because of the next error in line.
Don’t store an HttpClient instance inside an object

[ribesg]

@e5l it would be nice to have a warning of that somewhere, because you don’t expect an HttpClient to crash when it’s frozen. This is also the solution to https://github.com/ktorio/ktor/issues/887

[Ellen Shapiro]

@ribesg @gonzooin I got it working! a big piece of it was the fact that it was on an object, so thank you

[Ellen Shapiro]

The stuff that got frozen when it came back I was able to deal with by kicking back to Swift code

[Ellen Shapiro]

it’s cheating, but that’s my kind of cheating 🙂

[gonzooin]

Congrats on that 👏
We figured out by keeping a reference to httpClient from Swift ( for summarize the solution 😄 )

[e5l]

Awesome thanks for the investigation, probably I have an idea how to fix the issue with client in object and try to implement it in next release 🙂

[e5l]

https://youtrack.jetbrains.com/issue/KT-30454