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I'm trying to build a

List<List<Pacs>>

from a large

List<Pacs>

. I created a function

buildGroupedList

that takes

List<Pacs>

as argument.

class Foo(val bar: Boolean)

var foo: Foo? // initialized somewhere in the code

fun test(): Boolean {
    return foo != null && !foo!!.bar // doesn't look nice
}

How can I make the expression in test() method nicer assuming I can't make foo non nullable?

If I have an interface as

interface StringProvider {
  operator fun get(key: String): String
  fun getString(key: String): String
  ....
}

And I have a class that contains the key but can not add this

StringProvider

dependency how can I add this block to the constructor so I can get the key?

class Foo {
  ....
  var age: String
  var weigh: String
  fun getExample(provider: (String) -> String) : Foo { 
    age = provider["ageprovider"]
    weigh = provider["weighprovider"]
  }
}

So in my class that I have a object of

StringProvider

I send just the

StringProvider

Hi! Is it possible to collect the “StateFlow” in the same thread as producer? like in RxJava subjects? I’m trying to collect something using StateFlow but I’d like to do it in the producer thread. The collection execution code should block the producer if I do long running operations on the propagated value. The current implementation of flow forces us to use some kind of coroutine launchers for collection. Any help would be appreciated.

Hi all! Just for my sanity - am I seeing ghosts / am I doing something stupid or is this a real bug? https://youtrack.jetbrains.com/issue/KT-46947

Hi everyone! Is there any wrapper for

try { } catch (e: Exception) { }

block that returns

null

on exception (in stdlib)? Something like

runCatching { }

, but without unwrapping.

Hi 👋 Which channel would be the best to ask about the

@OptIn

annotation. I am looking for an enhancement and would like to know if it even makes sense before opening an issue.

why do fold and foldRight have their lambda parameters in a different order? (foldRight has acc first, and fold has it second)

How can I obtain a reference to a generic top level function? ie. something like this but working:

fun <R> foo(block: () -> R): R = TODO()

val fooName = ::foo.name

What do you prefer and why? 1️⃣

nullableBoolean == true

2️⃣

nullableBoolean ?: false

message has been deleted

is there release note of each version?

I keep seeing things about Kotlin compatibility with jspecify, which looks great. I'd like to use it, but the jspecify repo says it's WIP and I can't find any published builds. Where are you/where should I get the artifacts from?

how can I use

implementation project(":module")

in kotlin build script

How do I change this List<T>?

data class Foo (val id: String, val name: String)
val fooList = listof<Foo>(Foo("1","foo1"),Foo("2","foo22)

Imagine I get this

fooList

as a parameter and I want to update this list, do I need to do a

clone

of the list and then a

copy

of the

data class

and update there the values?

Can somebody explain, why

(0F/0F).coerceIn(0F,1F)

NaN

?

Help me please. I am trying to update kotlin plugin to version “1.5.10” from “1.4.32" and kotlinx-serialization-json to version “1.2.0” . After the update, the project stopped building - “java.util.NoSuchElementException: Collection contains no element matching the predicate. at org.jetbrains.kotlinx.serialization.compiler.backend.ir.IrBuilderExtension$DefaultImpls.serializableSyntheticConstructor(GeneratorHelpers.kt:1255)”

Hi! I'm trying to benchmark a possible extension for https://github.com/MicroUtils/kotlin-logging. This lib provides ideomatic logging like

<http://logger.info|logger.info> { "Some expensive $string" }

. Now there's structured logging as well with https://github.com/logstash/logstash-logback-encoder. It would be great if I could use the lazy evaluated logging approach with multiple arguments as well. I came up with something like

private fun KLogger.infoWithVarargSupplier(
        vararg arguments: () -> Any,
        message: () -> String,
    ) {
        if (isInfoEnabled) {
            info(
                message.invoke(),
                *arguments
                    .map { it.invoke() }
                    .toTypedArray(),
            )
        }
    }

and now I'd like if there would be any huge performance impact in using a function like this. I tried creating a JMH benchmark but the results look suspicious … any suggestions?

Hey All, silly newbie question here:

Would Kotlin be a good choice for developing an app that is essentially performing calculator and timer functions against data entries and automatic updates? ## App Basics • Mobile App: (IOS & Android, preferably) •

v1

 isn't expected to be much more than form pages for manual data entry and then a fairly simple algorithm against said data to produce a suggested number based on the input. During these events it will also kick off a timer to track the time since the input for later calculations. My 

v1

 architecture will likely be locally stored data (haven't decided on database type), which can be copied/saved to cloud storage providers (e.g., Google Drive, Box, OneDrive, etc.). The data needs to be encrypted for privacy. I'd like to collect anonymous usage statistics with zero private information and have that sent back to a web service that I intend to write—haven't decided on an event queue/bus service yet but will likely use something opensource initially. I ask because I believe a more native language would probably perform faster calculations and more reliable timers. Which is something I believe will become very important with later feature releases that are using more algorithms, and potentially AI/ML. (edited)

Is there a better way to have a Deferred<T> where the value is provided through a function call? I'm pretty sure this has a race condition with the exception that tells you the newMap you provided was never going to be used.

class MapboxState constructor(override val coroutineContext: CoroutineContext): CoroutineScope {
    private val mapChan = Channel<MapboxMap>(1)
    val map = async {
        mapChan.receive()
    }

    internal suspend fun registerMap(newMap: MapboxMap) {
        if (map.isCompleted) {
            throw IllegalStateException("MapState already registered to a MapboxMap")
        }
        mapChan.send(newMap)
    }
}

This message was deleted.

Hello! When bumping a project from Kotlin 1.3.60 to 1.5.10, the compiler seems to be erroring out with a java.lang.OutOfMemoryError. What can I do to analyze this further?

Is there a way to (locally) decorate an operator fun to take precedence over a builtin on the class? I'm writing test cases where overloading

get

makes sense, but some of the data I have to pass in are arrays. I can manually 'up' cast to Any, but I'm curious if there's any other possibility.

Hi, Has anyone encountered problems in the tests to cover lambdas in sonarqube? There are always cases without covering

Just ran across this, which throws an `UnsupportedOperationException`:

val list = listOf(1, 2)
if (list is MutableList) list.add(3)

https://pl.kotl.in/_jfhJy6is Why is that? I mean, I get that the list is immutable, but why then can it be cast to MutableList?

Hi guys I have made a Developer tool. Which is a search engine you can. There are 25+ Docs supported including Android, Flutter, React Native. For more info visit: https://www.producthunt.com/posts/devhuntr

I'm using something like this

backButton.setOnLongClickListener {
    GlobalScope.launch(Dispatchers.Main) {
        if (backButton.isPressed) {
            viewPager.setCurrentItem(viewPager.currentItem - 1, true)
            delay(500)
        }
    }
    true
}

Created a Question on stack overflow with a better description, https://stackoverflow.com/q/67741723/4083142