Kotlin Tutorials

Kotlin Set associateWith()
Syntax & Examples

Set.associateWith() extension function

The associateWith() extension function for sets in Kotlin returns a Map where the keys are elements from the set and the values are produced by the valueSelector function applied to each element.

Syntax of Set.associateWith()

The syntax of Set.associateWith() extension function is:

fun <K, V> Set<K>.associateWith(valueSelector: (K) -> V): Map<K, V>

This associateWith() extension function of Set returns a Map where keys are elements from the given set and values are produced by the valueSelector function applied to each element.

Parameters

ParameterOptional/RequiredDescription
valueSelectorrequiredA function that takes an element of the set and returns a value for the resulting map.

Return Type

Set.associateWith() returns value of type Map.


✐ Examples

1 Using associateWith() to create a map from a set of strings

In Kotlin, we can use the associateWith() function to create a map from a set of strings, where the keys are the strings and the values are their lengths.

For example,

  1. Create a set of strings.
  2. Use the associateWith() function with a valueSelector function that returns the length of the string.
  3. Print the resulting map to the console using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val fruits = setOf("apple", "banana", "cherry")
    val fruitLengths = fruits.associateWith { it.length }
    println("Fruit lengths: $fruitLengths")
}

Output

Fruit lengths: {apple=5, banana=6, cherry=6}

2 Using associateWith() to create a map from a set of integers

In Kotlin, we can use the associateWith() function to create a map from a set of integers, where the keys are the integers and the values are their squares.

For example,

  1. Create a set of integers.
  2. Use the associateWith() function with a valueSelector function that returns the square of the integer.
  3. Print the resulting map to the console using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val numbers = setOf(1, 2, 3, 4, 5)
    val squares = numbers.associateWith { it * it }
    println("Number squares: $squares")
}

Output

Number squares: {1=1, 2=4, 3=9, 4=16, 5=25}

3 Using associateWith() with an empty set

In Kotlin, we can use the associateWith() function to create a map from an empty set, which will result in an empty map.

For example,

  1. Create an empty set of integers.
  2. Use the associateWith() function with a valueSelector function that returns the square of the integer.
  3. Print the resulting map to the console using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val emptySet = emptySet<Int>()
    val squares = emptySet.associateWith { it * it }
    println("Number squares in empty set: $squares")
}

Output

Number squares in empty set: {}

Summary

In this Kotlin tutorial, we learned about associateWith() extension function of Set: the syntax and few working examples with output and detailed explanation for each example.