Hello! Can anyone tell me if there's a neater way of doing this? I'm trying to essentially run some code after a specified delay, but I want to handle the case the function is called before it's actually finished executing.

private var job: Job? = null
    private fun scheduleJob() {
        job?.cancel()
        job = flow<Void> {
            delay(mySpecifiDelay)
            doWork()
        }.launchIn(CoroutineScope(coroutineDispatcher))
    }

hi all, there any channel for Testing ( Unit Test ) ?

Hi all, Why Kotlin Any type has only 3 methods equals, hashCode and toString. While standard Java Object type has some additional ones like wait/notify

I'm planning to prepare a presentation for a KUG meeting on this topic: "_10 surprises when coming from Java to Kotlin_". Please share in this thread things that in your opinion would be worth mentioning in the presentation :) I have my thoughts, but reaching to the community because maybe I forgot about something important (started with Kotlin 4 years ago, might have forgotten something).

Can someone please help me with this? https://stackoverflow.com/questions/68511430/jackson-serialisation-fails-by-throwing-kotlinreflectioninternalerror-when-seria

Hi I am having a map like this: [ key1 : [1,2,3], key2: [2,3,4], key3: [3,4,5]] I would like to get a map like this: [1:[key1],2:[key1,key2],3:[key1,key2,key3],4:[key2,key3],5:[key3]] any suggestions on how to group by elements in a list and not the list itself? Thanks

how do i insert an unicode character literal, value of which is more than

0xffff

?

\U12345678

doesn't seem to work

Is there a way i can fix that?

Is there a way to force when statements to be exhaustive officially yet? I remember it was talked about. Right now I’m just putting a

.let {}

at the end of my when statements.

Hi, Do jetpack compose trustworthy for business applications? And can we publish an application written with Jetpack compose on Google Play?

Is it possible in Kotlin get function argument from function instance? For example i want kind of

retry

function

fun <T, R> ((T, R) -> Unit).retry() {
        this(argument1, argument2)
    }

My real case a bit more complicated, here just extraction for clear my question.

Hi, how can i make an universal comporator in kotlin?

fun<T : Comparable<T>, K> comparePairByFirst() : Comparator<Pair<T, K>>  = Comparator { p1, p2 -> p1.first.compareTo(p2.first) }

I have this code and it works, but creates a new similar comparator every use. I think it is bad. How can I make it better? ------------------------------------------------------------------------------------------------------------------------------------------------------------ How i can "this" method in inline functions? I want to get that class to log it.

Kotlin inline functions create a lot of copies of java-primitive types. Parameters in kotlin are final so java-primitive elements can not be changed. How can I fix it? Maybe by annotations or compiler flags?

Is it possible to count graphemes instead of characters in pure kotlin (one that works in both jvm and native)? I'm looking for something like this but for pure kotlin: https://stackoverflow.com/a/29743275/1118475. E.g. an emoji in utf16 will be counted as two characters with 

emojiText.length

 and I would like a method which returns 

1

.

Any idea, how to troubleshoot:

Error: Could not find or load main class org.jetbrains.kotlin.cli.jvm.K2JVMCompiler
Caused by: java.lang.ClassNotFoundException: org.jetbrains.kotlin.cli.jvm.K2JVMCompiler

1.5.21 gradle plugin, tried different SDKs, upgrading plugin to 1.5.30-M1, downgrading to 1.5.20, 1.5.10. Cleaning project, removing whole $HOME/.gradle directory. This error relates to submodule of multi-project project. Modules use either jvm or mpp plugin.

Java Interoperability question: Can’t we access Inline Value class fields and constructor from Java? In the below example I don’t get any compiler error but fails at runtime with

error: cannot find symbol

# Kotlin Value class

import io.vavr.control.Either
import io.vavr.kotlin.right

@JvmInline
value class Name(val s: String) {
    val length: Int
        get() = s.length
}

fun getAsName(): Either<String, Name> = right(Name("Kotlin"))

# Java Client

@Test
void testValueClass() {
  final var name = getAsName().get();
  Assertions.assertEquals(0, name.getLength());
}

# Error

error: cannot find symbol
    Assertions.assertEquals(0, name.getLength());
                                   ^
  symbol:   method getLength()
  location: variable name of type Name

hi i'm trying to reduce the visibility of an extension written to fragment. So this extension should be only visible at package level.

package com.abcd.registration
internal fun 

Fragment.showUserAlreadyRegisteredOnAnotherDevice(actionProceedToRegister: (() -> Unit)?,
                                                               actionCancel: (() -> Unit)?) {
    activity?.supportFragmentManager?.let {
        var alreadyRegisterAnotherDeviceBottomSheet: AlreadyRegisterAnotherDeviceBottomSheet =
                AlreadyRegisterAnotherDeviceBottomSheet.getInstance(
                        actionProceedToRegister,
                        actionCancel)

        alreadyRegisterAnotherDeviceBottomSheet?.show(it, "BottomSheet")
    }
}

I want this to be visible to only registration package any top level package should be able to use this extension even if they are inheriting from Fragment. Is this doable. I added internal keyword, still it is not working here. Any inputs ?

I have done the installation as per the instructions

Currently I’m trying to automate een excel task for my work in python but want to convert it to kotlin. I am using XLwings lib because this was the only lib that supports the xlsb format. Is there a way to automate it directly in kotlin or run the python script? the automations exist of opening a template, inserting data in 1 sheet, running a macro on another sheet and saving it with a custom name.

I simply want to ask why

toUpperCase()

and

toLowerCase()

got deprecated in

1.5

uppercase()

and

lowercase()

seems to have exactly same code, so why rename such a common method name after such stability of the language?

Hi everyone - I briefly wanted to mention that we released our first developer preview of the Couchbase Kotlin SDK: https://forums.couchbase.com/t/ann-couchbase-kotlin-sdk-1-0-0-dp-1/31223 - we’d love to get feedback! I created a #couchbase channel for it.

Are there currently any book recommendations? The docs are fantastic but I like diving into a book with some actual project examples 🙂

I just took the Kotlin badge test on LinkedIn. It doesn’t tell me the answers so I don’t know for sure. There are a LOT of small wording problems in the quiz where it’s not clear if they are trying to gotcha you or not. i.e. They show you a function and call it

shouldEqual

, but the correct answer calls the function

shouldMatch

. There were lots of small little mistakes in the correct answers that make you question whether or not it’s the correct answer.

So, I have these extension functions

@file:JvmName("UriDeepLinkFactory")
...
fun UriDeepLink.Companion.from(uri: Uri): UriDeepLink {
    return UriDeepLink(UriParameter(uri)) { scheme -> Schemes.valueOf(scheme) }
}
fun UriDeepLink.Companion.from(uriString: String): UriDeepLink {
    return UriDeepLink.from(Uri.parse(uriString))
}

But when I try to access it from java I get the error at compile time

final UriDeepLink deepLink = UriDeepLinkFactory.from(operationDeepLink);
                                                       ^
    method UriDeepLinkFactory.from(Companion,Uri) is not applicable
      (actual and formal argument lists differ in length)
    method UriDeepLinkFactory.from(Companion,String) is not applicable
      (actual and formal argument lists differ in length)

Any idea of how to fix it ?

I assume there is a bug somewhere between AS or the kotlin compiler? anything I can do besides having the warning for the time being?

Why doesn't this compile, it feels like it should?

abstract class A {
    open val x: String? = null
}

sealed class B : A() {
    override val x = "x"
}

class C : B() {
    override val x = null
}

If I add a type annotation on

B.x

of

String?

, then it works...

Like Kotlin, Swift supports implicit self/this. I ran a poll over in the Swift forums to see who embraced implicit, and who embraced explicit. I honestly expected implicit to be +95%. I was surprised that the breakdown was 29% explict, 71% implicit, out of 140 votes. I'm curious what the breakdown is in the Kotlin crowd. Poll: Implicit this = 🔵 (

:large_blue_circle:

), Explicit this = :large_green_square: (

:large_green_square:

)

Hi, why are the results different?

fun main() {
    val a: () -> Unit = { }
    val b: () -> Unit = { }
    val c = generateLambda()
    val d = generateLambda()

    println(a == b) // false
    println(c == d) // true
}

fun generateLambda(): () -> Unit {
    return { }
}

Struggling to understand why the overriding works with val but not with var. What changes with var? This works:

class A (
    override val values: List<A>
) : B

interface B {
    val values: List<B>
}

This does not:

class A (
    override var values: List<A>
) : B

interface B {
    var values: List<B>
}