How to convert list to map in Kotlin

Two ways to convert list to map in Kotlin, with code examples
31 October 2017   1934

For example, you have a list of strings like:

val list = listOf("a", "b", "c", "d")

and you need to convert it to a map, where the strings are the keys.

There are two ways to do this:

The first and most performant is to use associateBy function that takes two lambdas for generating the key and value, and inlines the creation of the map:

val map = friends.associateBy({it.facebookId}, {it.points})

The second, less performant, is to use the standard map function to create a list of Pair which can be used by toMap to generate the final map:

val map = { it.facebookId to it.points }.toMap()

JetBrains to Roll Out Kotlin/Native 0.8

Version 0.8 of Kotlin/Native brings new features and bug fixes
13 July 2018   278

The project team of Kotlin / Native introduced the release of version 0.8. Corrections and additions have concerned the security of multithreaded programming, the expansion of library functionality and support for iOS devices. As always, alot of bugs are fixed.


Implemented the concept of object freezing

object Config {
  var width: Int = 10
  private set
  init {
    val file = fopen("config.txt", "r")
    if (file != null) {
              try {
              val buffer = ByteArray(2 * 1024)
                 while (true) {
                 val nextLine = fgets(buffer.refTo(0), buffer.size, file)?.toKString()
                 if (nextLine == null || nextLine.isEmpty()) break
                 val records = nextLine.split('=')
                 if (records.size != 2) continue
                 val key = records[0].trim()
                 val value = records[1].trim()
                 when (key) {
                         "width" -> width = value.toInt()
             } finally {

This code considers the configuration file and will later receive the Config.width property. 

The Config file itself is divided for any number of threads or vorkers. After publication, the object is frozen and any attempt to change it will result in an exception (InvalidMutabilityException).

The second peculiarity of parallelism in the Kotlin / Native project is indivisible values and references. Let's add an image:

object Config {
private val icon_ = AtomicReference()
val icon: Image
get() = icon_.get()!!
fun updateIcon(file: String) {
val imageData = Image(file)
icon_.compareAndSwap(icon_.get(), imageData.freeze())

All information about the icon in the AtomicReference is frozen. Any changes are indivisible and similar information is visible to each client.

Kotlin Libraries

Starting v 0.8, the standard library (kotlin. *) is compatible with other platforms. Standard number generator and the function of mixing the collections are designed to eliminate the use of sharpened for a specific platform API. As an experiment, the project supports other libraries, for example, kotlinx.coroutines, kotlinx.serialization, and also the Ktor HTTP client.

Changes for iOS devices

Fixed issues with the publication in the App Store and the initialization of the platform. Support for the 32-bit ARM architecture of iOS processors, which allows using Kotlin / Native on older devices from Apple added.