associateByTo

Common
JVM
JS
Native
1.0
inline fun <T, K, M : MutableMap<in K, in T>> Array<out T>.associateByTo(
    destination: M,
    keySelector: (T) -> K
): M
inline fun <K, M : MutableMap<in K, in Byte>> ByteArray.associateByTo(
    destination: M,
    keySelector: (Byte) -> K
): M
inline fun <K, M : MutableMap<in K, in Short>> ShortArray.associateByTo(
    destination: M,
    keySelector: (Short) -> K
): M
inline fun <K, M : MutableMap<in K, in Int>> IntArray.associateByTo(
    destination: M,
    keySelector: (Int) -> K
): M
inline fun <K, M : MutableMap<in K, in Long>> LongArray.associateByTo(
    destination: M,
    keySelector: (Long) -> K
): M
inline fun <K, M : MutableMap<in K, in Float>> FloatArray.associateByTo(
    destination: M,
    keySelector: (Float) -> K
): M
inline fun <K, M : MutableMap<in K, in Double>> DoubleArray.associateByTo(
    destination: M,
    keySelector: (Double) -> K
): M
inline fun <K, M : MutableMap<in K, in Boolean>> BooleanArray.associateByTo(
    destination: M,
    keySelector: (Boolean) -> K
): M
inline fun <K, M : MutableMap<in K, in Char>> CharArray.associateByTo(
    destination: M,
    keySelector: (Char) -> K
): M

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function applied to each element of the given array and value is the element itself.

If any two elements would have the same key returned by keySelector the last one gets added to the map.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val charCodes = intArrayOf(72, 69, 76, 76, 79)
val byChar = mutableMapOf<Char, Int>()

println("byChar.isEmpty() is ${byChar.isEmpty()}") // true
charCodes.associateByTo(byChar) { Char(it) }

println("byChar.isNotEmpty() is ${byChar.isNotEmpty()}") // true
// L=76 only occurs once because only the last pair with the same key gets added
println(byChar) // {H=72, E=69, L=76, O=79}
//sampleEnd
}
Common
JVM
JS
Native
1.0
inline fun <T, K, V, M : MutableMap<in K, in V>> Array<out T>.associateByTo(
    destination: M,
    keySelector: (T) -> K,
    valueTransform: (T) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> ByteArray.associateByTo(
    destination: M,
    keySelector: (Byte) -> K,
    valueTransform: (Byte) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> ShortArray.associateByTo(
    destination: M,
    keySelector: (Short) -> K,
    valueTransform: (Short) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> IntArray.associateByTo(
    destination: M,
    keySelector: (Int) -> K,
    valueTransform: (Int) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> LongArray.associateByTo(
    destination: M,
    keySelector: (Long) -> K,
    valueTransform: (Long) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> FloatArray.associateByTo(
    destination: M,
    keySelector: (Float) -> K,
    valueTransform: (Float) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> DoubleArray.associateByTo(
    destination: M,
    keySelector: (Double) -> K,
    valueTransform: (Double) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> BooleanArray.associateByTo(
    destination: M,
    keySelector: (Boolean) -> K,
    valueTransform: (Boolean) -> V
): M
inline fun <K, V, M : MutableMap<in K, in V>> CharArray.associateByTo(
    destination: M,
    keySelector: (Char) -> K,
    valueTransform: (Char) -> V
): M

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function and and value is provided by the valueTransform function applied to elements of the given array.

If any two elements would have the same key returned by keySelector the last one gets added to the map.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val charCodes = intArrayOf(65, 65, 66, 67, 68, 69)

val byUpperCase = mutableMapOf<Char, Char>()
charCodes.associateByTo(byUpperCase, { Char(it) }, { Char(it + 32) })

// A=a only occurs once because only the last pair with the same key gets added
println(byUpperCase) // {A=a, B=b, C=c, D=d, E=e}
//sampleEnd
}
Common
JVM
JS
Native
1.0
inline fun <T, K, M : MutableMap<in K, in T>> Iterable<T>.associateByTo(
    destination: M,
    keySelector: (T) -> K
): M

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function applied to each element of the given collection and value is the element itself.

If any two elements would have the same key returned by keySelector the last one gets added to the map.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
data class Person(val firstName: String, val lastName: String) {
    override fun toString(): String = "$firstName $lastName"
}

val scientists = listOf(Person("Grace", "Hopper"), Person("Jacob", "Bernoulli"), Person("Johann", "Bernoulli"))

val byLastName = mutableMapOf<String, Person>()
println("byLastName.isEmpty() is ${byLastName.isEmpty()}") // true

scientists.associateByTo(byLastName) { it.lastName }

println("byLastName.isNotEmpty() is ${byLastName.isNotEmpty()}") // true
// Jacob Bernoulli does not occur in the map because only the last pair with the same key gets added
println(byLastName) // {Hopper=Grace Hopper, Bernoulli=Johann Bernoulli}
//sampleEnd
}
Common
JVM
JS
Native
1.0
inline fun <T, K, V, M : MutableMap<in K, in V>> Iterable<T>.associateByTo(
    destination: M,
    keySelector: (T) -> K,
    valueTransform: (T) -> V
): M

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function and and value is provided by the valueTransform function applied to elements of the given collection.

If any two elements would have the same key returned by keySelector the last one gets added to the map.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
data class Person(val firstName: String, val lastName: String)

val scientists = listOf(Person("Grace", "Hopper"), Person("Jacob", "Bernoulli"), Person("Johann", "Bernoulli"))

val byLastName = mutableMapOf<String, String>()
println("byLastName.isEmpty() is ${byLastName.isEmpty()}") // true

scientists.associateByTo(byLastName, { it.lastName }, { it.firstName} )

println("byLastName.isNotEmpty() is ${byLastName.isNotEmpty()}") // true
// Jacob Bernoulli does not occur in the map because only the last pair with the same key gets added
println(byLastName) // {Hopper=Grace, Bernoulli=Johann}
//sampleEnd
}