Just a quick question, is there any more simpler way to write

list.sortedBy { it }

, for a list of strings or numbers ? I know it's already pretty short but the fact that there's only

it

in the lambda feels kinda wrong

Hi all, how fun is kotlin functional? given a list of items how can you return a list grouped by consecutive items? [“Apple, Bananas, Bananas, Orange” ] should return [(apple, 1), (bananas, 2), (orange, 1) ] I know you could use group by , but it does not respect the order

Is there an easy way to go from Instant to XMLGregorianCalendar in Kotlin?

What would be the best way to generate Kotlin programs? E.g. an AST API which can be used to generate kt files or do compiler validation with

I am trying to understand how I can rebuild a tree from a flat list which is given to me by an API. My model is simple:

data class Reply(id: Int, parentId: Int, replies: List<Reply>)

... and I'm attempting to:

{
    "replies": [
        { id: 1, parent: 0 }  <- turn this     1
        { id: 2, parent: 1 }     into this ->  └── 2
        { id: 3, parent: 2 }                       ├── 3
        { id: 4, parent: 3 }                       │   └── 4
        { id: 5, parent: 2 }                       ├── 5
        { id: 6, parent: 2 }                       ├── 6
        { id: 7, parent: 2 }                       └── 7
    ]
}

does anyone have any experience in "unflattening" a list into a tree like this? I start out by using

associateBy

on my flat list and turn it into a mutable map, at which point I iterate the flat list itself and append the current item to any value in the map whose

id

matches the current iterator item's

parentId

. doing this I end up with a list where the first and second levels are correct, but third and deeper are empty I've spent about 10 hours on this over the past 3 days and I've really gotten nowhere, just going in circles really. would love some guidance from anyone who has done this kind of thing with Kotlin

Hi everyone! Lets say I have the following structure:

class Test {
    val firstValue: String
    val secondValue: Long
}

class TestWrapper {
    val firstValue: Wrapper<String>
    val secondValue: Wrapper<Long>
}

Would it be possible somehow to create a common interface/class for these two classes? For example, if it would be possible, using union types:

interface InterfaceTest<T : Wrapper<T>, T>

But given that is not possible, is it some other way Kotlin can handle this?

Hi everyone! If some 3rd party lib is providing the following couple of functions:

fun find(session: Session, query: Query) {}
fun find(query: Query) {}

Is there a cleaner way than this to pick which one to use?

fun caller(session: Session?) {
    val query = Query()
    if (session == null) {
        return find(query)
    }
    return find(session, query)
}

Thanks!

i have a question about suspend functions and await (thread)

I have a very simple question. I have a kotlin multiplatform gradle project. I use VS Code and the command line to run and build it. When I run

./gradlew --version

I get

------------------------------------------------------------
Gradle 6.8.1
------------------------------------------------------------

Build time:   2021-01-22 13:20:08 UTC
Revision:     31f14a87d93945024ab7a78de84102a3400fa5b2

Kotlin:       1.4.20
Groovy:       2.5.12
Ant:          Apache Ant(TM) version 1.10.9 compiled on September 27 2020
JVM:          11.0.10 (JetBrains s.r.o. 11.0.10+0-b96-7249189)
OS:           Mac OS X 12.1 aarch64

Where does the Kotlin version

1.4.20

come from and how to I update that version? I don’t have that version specified anywhere in my project. In fact, I’m using

1.6.20

for kotlin-multiplatform. How do I set Kotlin to the same version? Thanks!

Hey — I have a module system in my project which allows me to write generalized extensions and features for my project. At the moment I register these modules by manually adding it to a list in a manager class. I want to try to clean up this process a bit by adding an

@Register

annotation which allows the manager class to automatically register it. While I could do this with reflection, I want to be able to include and exclude some of these modules at compile-time (IE if I have a beta vs prod build), and preferably also generate the list at compile-time. from what I can tell, the best way to do this is with a compiler plugin, but I can’t find a framework which allows this as most major Kotlin compiler plugin libraries don’t allow modifying existing files, but instead only creating new ones. How should I go about doing this?

Hi, i have a KMM library which uses cocoapods for the ios targets (arm64, simarm64) and when trying to compile its failing because of Unresolved reference: cocoapods BUT when i set one ios target, then it seems to work, but obviously i need to support multiple targets.

If you have a Java interface

public interface Transformer<OUT, IN> {
    OUT transform(IN in);
}

And a Java method

filter(Transformer<String, String> var1)

And Kotlin wrongly assumes the second parameter to be non-

null

. How can you call it with a lambda that returns

null

?

What resources do you have for “compose for desktop” beginners?

And what resources would you recommend for newcomers to Kotlin because YouTube isn't working out

Hi, can I create an extension static method to all classes ? I tried this

inline fun <T : Any> T.create(block: T.() -> Unit) = jso(block)

But the receiver type is of the companion object of the class and doesn't work if the class doesn't have any companion object, so this is not what I want I want to be able to do

AnyClass.create { }

and have the receiver equal to the receiver when doing

AnyClass().apply { }

Hi, Does Jetbrains have a slack channel for IDEs too? I have questions about Rider for .Net and code style

Hello, I'm new to Kotlin and I'm trying to code an application with the IDE AndroidStudio. I would like to recover a csv file send by an other application thus I would like that my application shows in the selection area of the other application ( like Gmail in the ScreenShot). Do you you know how I can do this ? Or do you have any link that explain how to do it ?

Need help in building the algorithm, looking for an optimum version of it,

The logic for creating the fixture is in pairs. You have to form a pair of two teams in a random                                     
fashion. For example - If I have 4 teams - T1, T2, T3, T4. I can have: 
 
(T1 vs T2) & (T3 vs T4) 

OR 
(T1 vs T3) & (T2 vs T4) 

OR 
(T1 vs T4) & (T2 vs T3) 
 
*Your function should accept any number n, where n is an even number > 0 and return you n/2                               
pairs/tuples*

Hello, is it currently possible to use Compose for Kotlin Multiplatform to create a common module which can provide Composables to both Kotlin/JVM for Desktop and Kotlin/JS for Web modules? The use case for this would be to create a UI that is consistent across both Desktop and Web without having to recreate UI models separately per platform. I am aware data models can be designed and shared using the architecture stated above but am unsure whether shared composables can be used in the same way. Is it possible to have a module with both jvm + js targets which imports and compiles "org.jetbrains.compose" and creates all the artifacts needed for both JVM and JS modules?

Hi, I fell into a little types mangling while doing a library for Kotlin/JS, I typed some events types that uses

eventemitter3

library with a pretty ugly (I think) but simple solution

sealed interface DisplayObjectEvents<T : Any> {
	object added : DisplayObjectEvents<Container>
	object click : DisplayObjectEvents<FederatedPointerEvent>
	object clickcapture : DisplayObjectEvents<FederatedPointerEvent>
	object destroyed : DisplayObjectEvents<Nothing>
	object mousedown : DisplayObjectEvents<FederatedPointerEvent>
    ...
	(there are almost 100 elements in total)
}

But I want to be able to use it like that

myObject.on<DisplayObjectEvents.added> { // it is Container here }

, so I created this

inline fun <reified T : DisplayObjectEvents<T>> DisplayObject.on(noinline callback: (T) -> Unit) = on(T::class.simpleName!!, callback as ListenerFn, null)
// ListenerFn is just a function type that take Any arguments Any number of time
// Which is the default type for my library for events in TypeScript

But

myObject.on<DisplayObject.added> {
    // it is of type DisplayObject.added
}

What I've done wrong ?

in Kotlin, what is the most efficient way to replace many strings inside another string? what I mean is, I could do:

originalString
    .replace("cat", "dog")
    .replace("goat", "cow")
    .replace("horse", "pig")

..but chaining those

replace()

calls would become very inefficient I assume, even if I created a map to iterate over. does Kotlin have any functions I can use to do a single pass over

originalString

and replace X number of items?

Can we do a conditional chain in Kotlin? or ignore it and go to the next operator?

private fun simulateFixtures(list: List<List<Team>>) = list.map { fixture ->
    fixture.toList().random()
}.shuffled().chunked(2)

How do I convert a

List<Int>

to an

IntArray

(not

Array<Int>

)?

Is there a ready function in std lib which maps a value from one range (say

0..1

) to another range (say

1_000..5_000

)? Basically the equivalent of this:

fun getRangeValueAtInterval(start: Int, end: Int, interval: Float): Int =
    start + (interval * (end - start)).roundToInt()

I have a class that does not take any parameters when instantiating, but it has a number of properties I need to set after. Is there any clean way to use a lambda or similar to set all of the properties inside one

{}

block after instantiating the class?

I'm curious why does Kotlin create a class implementation instead of default methods when creating an interface with methods that have a body? (I now you can change that)

Hi! How can I use generic type parameters in lambda types? For example:

val list = listOf<<T>(x: T) -> Unit>()

Hi everyone I would like to try to work with the kotlin AST but I have no idea where to start. Do you have any suggestions / links?

Hi. I have some questions about my Kotlin carrier. Is there an expert to help me? 😊