I would like to remove elements from a collection, based on a condition. For a list, we can use:

myList.removeAll { it.myField != myFieldValue }

But for a map, there doesn’t seem to be

removeAll

:

myMap.removeAll { it.key != myKeyValue }    <--- removeAll doesn't exist

what should I use instead?

Not new to Kotlin but new to Flow. Is there a way to rewrite the following code to make it shorter, or do I need to resort to writing my own extension? I need to emit null when the list is empty

I was told that there was a place where I can see the implementation of functions in Kotlin's standard library. I was wondering if that was a place in the Kotlin docs, or do I somehow inspect the code in IntelliJ to get the implementation?

I have a gradle project with Kotlin 1.5.10. IDEA doesn't find

@JvmInline

, and says I should add

kotlin-stdlib:1.4.31

to the class path. Is there something hidden somewhere in the settings?

Is there anyway in Kotlin to have two constructors in class with both having lists as an argument but with different types in them? For example:

constructor(aList : List<A>)  /* Main constructor */
constructor(bList : List<B>) : this (bList.toListA())

I get the following:

Platform declaration clash: The following declarations have the same JVM signature ((Ljava/util/List;)V):

How do I distinguish between them?

how to set the kotlin version in gradle file? This is my build.gradle.kts:

import org.jetbrains.kotlin.gradle.targets.js.webpack.KotlinWebpack

plugins {
  kotlin("multiplatform") version "1.5.10"
  kotlin("plugin.serialization") version "1.5.10"
  application
}

group = "tech.tarunchawla"
version = "0.0.1"

repositories {
  jcenter()
  mavenCentral()
  maven { url = uri("<https://dl.bintray.com/kotlin/kotlin-js-wrappers>") }
  maven { url = uri("<https://dl.bintray.com/kotlin/kotlinx>") }
  maven { url = uri("<https://dl.bintray.com/kotlin/ktor>") }
  maven("<https://dl.bintray.com/konform-kt/konform>")
}

kotlin {
  jvm {
    compilations.all {
      kotlinOptions.jvmTarget = "1.8"
    }
    testRuns["test"].executionTask.configure {
      useJUnit()
    }
    withJava()
  }
  js(LEGACY) {
    browser {
      binaries.executable()
      webpackTask {
        cssSupport.enabled = true
      }
      runTask {
        cssSupport.enabled = true
      }
      testTask {
        useKarma {
          useChromeHeadless()
          webpackConfig.cssSupport.enabled = true
        }
      }
    }
  }
  sourceSets {
    val commonMain by getting {}
    val commonTest by getting {
      dependencies {
        implementation(kotlin("test-common"))
        implementation(kotlin("test-annotations-common"))
      }
    }
    val jvmMain by getting {
      dependencies {
        implementation("io.ktor:ktor-server-netty:1.6.0")
        implementation("io.ktor:ktor-html-builder:1.6.0")
        implementation("org.jetbrains.kotlinx:kotlinx-html-jvm:0.7.2")
        implementation("io.ktor:ktor-gson:1.6.0")
        implementation("io.ktor:ktor-auth:1.6.0")
        implementation("io.ktor:ktor-auth-jwt:1.6.0")
        implementation("io.ktor:ktor-serialization:1.6.0")
        implementation("org.postgresql:postgresql:42.2.20")
        implementation("org.jetbrains.exposed:exposed-core:0.31.1")
        implementation("org.jetbrains.exposed:exposed-jdbc:0.31.1")
        implementation("org.jetbrains.exposed:exposed-java-time:0.31.1")
        implementation("com.auth0:java-jwt:3.10.3")
      }
    }
    val jvmTest by getting {
      dependencies {
        implementation(kotlin("test-junit"))
        implementation("org.xerial:sqlite-jdbc:3.34.0")
      }
    }
    val jsMain by getting {
      dependencies {
        implementation("io.ktor:ktor-client-js:1.6.0")
        implementation("io.ktor:ktor-client-serialization:1.6.0")
        implementation("org.jetbrains.kotlin-wrappers:kotlin-react:17.0.2-pre.206-kotlin-1.5.10")
        implementation("org.jetbrains.kotlin-wrappers:kotlin-react-dom:17.0.2-pre.206-kotlin-1.5.10")
        implementation(npm("react", "17.0.2"))
        implementation(npm("react-dom", "17.0.2"))
        implementation("org.jetbrains.kotlin-wrappers:kotlin-styled:5.3.0-pre.206-kotlin-1.5.10")
        implementation(npm("styled-components", "~5.3.0"))
        implementation("org.jetbrains.kotlin-wrappers:kotlin-react-router-dom:5.2.0-pre.206-kotlin-1.5.10")
        implementation("org.jetbrains.kotlin-wrappers:kotlin-redux:4.0.5-pre.206-kotlin-1.5.10")
        implementation("org.jetbrains.kotlin-wrappers:kotlin-react-redux:7.2.3-pre.206-kotlin-1.5.10")
        implementation("org.jetbrains.kotlinx:kotlinx-datetime:0.2.1")
        implementation("io.konform:konform-js:0.2.0")
      }
    }
    val jsTest by getting {
      dependencies {
        implementation(kotlin("test-js"))
      }
    }
  }
}

application {
  mainClass.set("MainKt")
}

tasks.withType<Jar> {
  manifest {
    attributes["Main-Class"] = "MainKt"
  }
  from(sourceSets.main.get().output)

  dependsOn(configurations.runtimeClasspath)
  from({
    configurations.runtimeClasspath.get().filter { it.name.endsWith("jar") }.map { zipTree(it) }
  })
}

tasks.getByName<KotlinWebpack>("jsBrowserProductionWebpack") {
  outputFileName = "output.js"
}

tasks.getByName<Jar>("jvmJar") {
  dependsOn(tasks.getByName("jsBrowserProductionWebpack"))
  val jsBrowserProductionWebpack = tasks.getByName<KotlinWebpack>("jsBrowserProductionWebpack")
  from(File(jsBrowserProductionWebpack.destinationDirectory, jsBrowserProductionWebpack.outputFileName))
}

tasks.getByName<JavaExec>("run") {
  dependsOn(tasks.getByName<Jar>("jvmJar"))
  classpath(tasks.getByName<Jar>("jvmJar"))
}

Cross-posting from #opensource. I'm new and hopefully doing this right.

Hi everyone. I think this channel is the right place to ask but let me know if I should move the conversation elsewhere... Basically I am interested in picking up Android development but know nothing about Kotlin. I programmed in Java a long time ago (Java 5/6 so a long time ago!) however can't remember anything from back then. I've also done C++ (98 nothing modern) for Windows desktop application development (MFC 😩) back in the early 2000s (around when .NET came out). Again I don't remember language specifics just general programming concepts. I am wondering what is the best approach for me to go about teaching myself Kotlin and refreshing DS&A and some programming related maths I have long forgotten?

how to create a blocking call without using thread and runblocking? Usecase is I want to use something instead of

thread { ... }

in this code: https://pastebin.com/d9xvi3ay When using

thread

Timber Logging library incorrectly assigns Tag. Like even when using Timber.d from Acitivity or other class, it will show Tag of Application class (where Timber is initialized)

I would like to express a suspend function as a callback:

suspend fun getMyObject() : MyObject {
   ...
   return myObject
}

val myApp = myCallback { myObject ->
   /* code using myObject */
}

how should I write the function 

myCallback

?

Hi 👋 looking for some help please, i'm new to Kotlin and React and trying to use an external JS lib https://github.com/tailwindlabs/headlessui

any help much appreciated. thanks

Hey everyone! This is my first time using Slack and I am also a beginner with Kotlin, so let me know if this question should go somewhere else. My question is: is Kotlin/Native for iOS “safe” to get started with given the memory management redesign? I am confused about whether or not code will have to be rewritten for Kotlin Multiplatform Libraries/modules once the iOS memory management redesign is released. Thanks!

hi! can i declare something like

some.thing.like

as

one

without doing

val one = some.thing.like

?

This message was deleted.

Hello, everyone! Question about work around exceptions in KMM Is there any good articles about best practices to work with NSError? is

localizedDescription

- best way to differ exceptions?

Hi, why is spread operator not work with split(): https://pl.kotl.in/5xrsPYB2c

Is it somehow possible to create an operator extension function is the underlying Java class already defines the operator as a regular function (minus in this example):

operator fun SomeClass.minus(b: SomeClass) = minus(b)

when I declare a class

MyClass

and an interface

MyInterface

and have several classes extending and implementing them, Kotlin infers both the class and the interface in generic types. For example

val list = listOf(ImplemA(), implemB())

contains objects that are

MyClass

and comply with

MyInterface

. IDEA describes the bound as

<{MyClass & MyInterface}>

in that case. Can I specify a type like that explicitly, without creating a new class? What's the catch?

Hello everyone, I was playing around with val functions and I ran into this problem ... could someone help me understand why the e option doesn’t work (which would seem the most reasonable) and why all the above works? https://pl.kotl.in/YdmU2qEUy

Hello everyone! How to use property from object? Code in 🧵

Is there a way to have a function return a function with a generic type in Kotlin? I want to do

fun doSomething(): (Class<T>) -> T {}

However because lambda expressions can't have generic types, this doesn't compile for me.

What this "some overhead" is? So, the sequences let you avoid building results of intermediate steps, therefore improving the performance of the whole collection processing chain. However, the lazy nature of sequences adds some overhead which may be significant when processing smaller collections or doing simpler computations. Hence, you should consider both Sequence and Iterable and decide which one is better for your case. https://kotlinlang.org/docs/sequences.html#construct

something really weird is happening here https://paste.ofcode.org/uf6LdvHyQQfTpNYmVKR2nE

is there any built-in util method from converting an outputstream to an inputstream?

I have a spring boot application and its memory usage is constantly growing. How to start looking what might be the cause of this?

I'm pretty much a brand new programmer. I've been sucked into this loophole of not being able to decide what language to use. I like the idea of Kotlin, but the people I've spoke with have told me that it is not beginner-friendly and that there are too many quirks in the language for it to be my first language/you need to know Java beforehand, and that I'd be better off with Python/JavaScript. Also, that the community isn't large enough to have the answers to my questions. Could anybody clarify these rumors and help me get out of this awful loophole! Thanks! 🙂

does this

typealias Visitor<T> = (TreeNode<T>) -> Unit

mean, “any function that takes TreeNode<T> and return Unit can now be referred to as

Visitor<T>

? so instead of writing

fun search(printResult: (TreeNode<T>) -> Unit)

I write

fun search(visit: Visitor<T>)

i'm trying to offer two methods with similar signatures:

inline fun <reified T : Any> queryParam(key: String) = ...
fun queryParam(key: String) = ...

in kotlin this works fine, but both mockk and mockito get confused, it's random which one of the methods get picked. is there any way of dealing with this?