Is it possible to specify the type of a function reference in the very same expression I'm referencing in? for example, instead of

val function: ((Char) -> Unit) = ::println
println(function)

something like

println(::println) // but this fails because it's ambiguous

Hi everyone. I always face difficulty to understand the context written in the documentation especially when the sentences contain of some terms. Examples like the Kotlin or Golang documentation. Does it mean I'm still not familiar with the terminology? How can I improve?

We are all geared up for our September Event going live in 90 minutes. We will have Carlos Mota and @Wajahat Karim speaking on Scoped Storage in Android and Building a Game 🎮 with Jetpack Compose. Register now if you haven't already at https://www.meetup.com/Kotlin-Mumbai/events/273000330/

is there any logging solution for Kotlin able to perform a NOP through configuration? I'm currently using SLF4J, with calls like

<http://logger.info|logger.info>("${PERFORM POTENTIALLY EXPENSIVE LOGGING OP}")

, so even if I configure the logger to only log errors, the info call will still incur the cost of the expensive operation, with no message being logged. Would be nice to have it so the logging doesn't even happen at all unless I turn it on.

anyone now is there is a slack for netty (not a kotlin questions obs)?

Does anyone know of a web-scraping library that supports Kotlin Multiplatform? I just need to parse

<meta>

tags on a webpage.

Does kotlin have a specific function to convert from

List<Char>

to

String

or should we just use

joinToString

? I’m trying to shuffle letters in a word and I’m doing so by

String.toList().shuffled()

Anybody experiencing the same (infinite analyzing) in IJ Ultimate (2020.2.2)? Tried different version of Kotlin plugin

I would like to write a GUI desktop application for macOS and I want to have an icon in the top menu bar (like the time machine icon) as well as use the notification system. Can I do this in Kotlin? Do I need to use Kotlin native?

considering the following code:

val hasMyPredicate = someObject.someField.hisField.finalField != null
val someOtherBoolean = extensiveFunction()
when{
    hasMyPredicate && someOtherBoolean -> {...}
    !hasMyPredicate && someOtherBoolean -> {...}
    !hasMyPredicate && !someOtherBoolean -> {...}
    hasMyPredicate && !someOtherBoolean -> { val value = someObject.someField.hisField.finalField //value is nullable here, but the precondition made sure that it isn't }
}

How can I reference a deep inner value to be non-null and then when accessed it is autotyped to be non-null I absolutely hate using !! and especially error("...") if the chain of access calls are all on non-settable values (they are all val)

hi all! I'm having the following code:

object A {
	val a = ...

   object B {
    	val b = ...
   }
}

and I'm accessing b like this:

A.B.b

(which is what I need) but I would like to move class B into another file, and still acces

b

the same way and I can't find the right way to define it I would like to have something like bellow (this is not a valid code):

object A.B {	
    val b = ...
}

Is there a way to get something similar? Thank you in advance!

Hey I’m coming from Typescript and Im trying to figure out how to “translate” some typings into Kotlin. I currently have this in Typescript code snippet where I am defining an interface general (

Version

) which can be extended to defined a specific object structure. I then have a defined type

VersionDefinition<V extends Version>

which has a simple data structure to it but it is restricted to implement the keys of the specified version (

[x in keyof V]

)

// Defining a map interface of a key type string and value type of any
interface Version {
 [key: String]: any
}

// Defining an object type that enforces the implementation of the specified version (V)
type VersionDefinition<V extends Version> = {
 [x in keyof V]: {
   description: String,
   headerName: FakeHeader,
 }
}
// Version 1 interface
interface Version1 extends Version {
 foo: Integer,
 bar: Integer,
 ...
}

// Version 1 implementation
const VERSION_1_DEFINITION: VersionDefinition<Version1> = {
 foo: {
   description: "Bar description",
   headerName: FakeHeader.FOO
 },
 bar: {
   description: "Bar description",
   headerName: FakeHeader.BAR
 }
 ...
}

I know I can create the

Version1

interface as a data class in Kotlin but my question then is there a way to create something similar to the

VersionDefinition<V extends Version>

where it enforces you to implement the keys of some interface, data class or map?

to what advantage?

i'm trying to write my own logging utility. is there anyway to use reified functions / extension functions to automatically get the calling classes name? something like

// usage
MyLogger.log("foo")

// impl
inline fun <reified T : Any> T.log(msg: String) {
  // ...
  val caller = T::class.simpleName
}

What is the Kotlin team focusing on more? JS or WASM? I wonder which one should be preferred for multiplatform applications

Hey hey, I’m doing something I feel should be much easier than how I’m doing it. I have an abstract class with some basic storage logic for domain entities:

abstract class ESGenerics<IDType : DomainID, EntityType : Entity>(
  private val elasticsearchClient: RestHighLevelClient,
  private val objectMapper: ObjectMapper
) {
   // ...
}

All Entity classes has an ID member that should always extend DomainID, so I made this:

interface Entity {
  val id: DomainID
}

These functions need EntityType and IDType as types for arguments. Now I feel like I shouldn’t have to pass the IDType to ESGenerics. After all, the EntityType always has an ID field with the correct type. But I can’t figure out how to access the type of EntityType’s ID member in a function declaration. I’d like to rewrite it from:

fun getByIDs(ids: List<IDType>): List<EntityType> {

To:

fun getByIDs(ids: List<EntityType::id>): List<EntityType> {

How can I do that?

are there other multiplatform testing libraries out there, or is it basically just

kotlin.test

? I miss AssertJ...

#general Since Kotlin Multiplatform is all over news, what do you have your say about it? Is it good to learn it?

given that

plus

has a single element overload, what's the reason for plusElement existing?

If I have a constant like:

const val DEBUG = false

and then code like:

if (DEBUG) {
  println("Addthread: $thread")
}

If

DEBUG

is set to false, will the `println`s be totally compiled out of the class file?

I need block an OkHttp Interceptor to wait other async operation return another Response with the same Chain. Is runBlocking the better way to do that? Below is my current implementation. It's working but I'm in doubt if there is a better way without block many parallel requests.

internal class CustomInterceptor(
    private val processor: Something
) : Interceptor {
    override fun intercept(chain: Interceptor.Chain): Response {
        val response = chain.proceed(chain.request())
        // FIXME: is this fine? Can this throw Socket timeout?
        return runBlocking(Dispatchers.Default) {
            processor.suspendUtilHaveAnotherResponseOrThrow(response, chain)
        }
    }
}

Anyone else has an issue with formatting 'when' statements after upgrading to kotlin 1.4.0+? There is a setting

Align when branches in columns

which is broken for us after the update. Please see the screenshots for actual and expected behavior.

Hi. I have some code that writes to an

OutputStream

, and some code that needs that data but wants to read from an

InputStream

. I came up with this but I was wondering if maybe thre's a more straightforward solution:

/**
 * Pipe output to an input stream. Uses a thread to write from output to input.
 * See: <https://stackoverflow.com/questions/5778658/how-to-convert-outputstream-to-inputstream>
 */
fun ByteArrayOutputStream.asInputStream(): InputStream = PipedInputStream().also { istream ->
    PipedOutputStream(istream).let { ostream ->
        Thread { ostream.use { writeTo(ostream) } }.start()
    }
}

Thanks!

Hello, does anybody know why the first timeout coroutine is not being cancelled when the second one gets a results and forces all children cancellation of the context?

class Test(val callbackWork: CustomCallbackWork) : CoroutineScope {
    private var job = Job()
    override val coroutineContext: CoroutineContext
        get() = <http://Dispatchers.IO|Dispatchers.IO> + job

    fun start() : Flow<Unit> {
        return channelFlow {
            launch {
                delay(5000)
                logger().d("After delay, isActive: $isActive")
                close()
            }

            launch {
                callbackWork.apply {
                    onSuccess = {
                        offer(Unit)
                        coroutineContext.cancelChildren()
                    }
                    onError = {
                        offer(Unit)
                        coroutineContext.cancelChildren()
                    }
                }
            }
        }
    }
}

The log is printed (obviously displaying

isActive=true

) after 5 seconds even though

onSuccess

is triggered before that delay. However, if I get the reference of the first Job and cancel it below, it works perfectly. What's wrong in the code?

Hi guys, newbie question about kotlin comparison. I want to create a data class that has some fields. And I want to make this comparable. I know I can implement Comparable interface. Is there facility in kotlin to implement the compareTo function? I see there is a compareValuesBy I can use but it wanted to avoid to do compareValuesBy for every field. What am I missing?

Hi guys, I work for a banking company and we are looking at Kotlin multiplatform but a stumbling block is code obfuscation... has anyone managed to solve this issue? we use arxan for both iOS and Android

Hello!! I’m trying to get an objects class by its class name and its throwing a class not found exception

Class.forName("com.mystuff.stylopoc.core.Features.Login")

I think its worth noting that the object, Login, is internal to a sealed class, Features Any ideas?

really simple programming question: whats the most elegant way to pad out a list with its own elements until a given size is reached? eg:

conciseExpr(listOf("A", "B"), 5) //output: [A, B, A, B, A]
conciseExpr(listOf("A", "B"), 2) //output: [A, B]
conciseExpr(listOf("A", "B"), 1) //output: [A]

you are gaurenteed that the input list is non-empty so far I'm working with

val output = inputList
        .let { partial -> (0 until 1+(inputTargetSize / partial.size)).map { partial }.flatten() }
        .take(inputTargetSize)

but i feel like

0 until 1+expr

is cloogy