ifEmpty

Common
JVM
JS
Native
1.3
inline fun < C , R > C . ifEmpty (
defaultValue : ( ) -> R
) : R where C : Array < * > , C : R

(source)

Returns this array if it's not empty or the result of calling defaultValue function if the array is empty.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val emptyArray: Array<Any> = emptyArray()

val emptyOrNull: Array<Any>? = emptyArray.ifEmpty { null }
println(emptyOrNull) // null

val emptyOrDefault: Array<Any> = emptyArray.ifEmpty { arrayOf("default") }
println(emptyOrDefault.contentToString()) // [default]

val nonEmptyArray = arrayOf(1)
val sameArray = nonEmptyArray.ifEmpty { arrayOf(2) }
println("nonEmptyArray === sameArray is ${nonEmptyArray === sameArray}") // true
//sampleEnd
}
Common
JVM
JS
Native
1.3
inline fun < M , R > M . ifEmpty (
defaultValue : ( ) -> R
) : R where M : Map < * , * > , M : R

(source)

Returns this map if it's not empty or the result of calling defaultValue function if the map is empty.

import kotlin.test.*
import java.util.*

fun main(args: Array<String>) {
//sampleStart
val emptyMap: Map<String, Int> = emptyMap()

val emptyOrNull = emptyMap.ifEmpty { null }
println(emptyOrNull) // null

val emptyOrDefault: Map<String, Any> = emptyMap.ifEmpty { mapOf("s" to "a") }
println(emptyOrDefault) // {s=a}

val nonEmptyMap = mapOf("x" to 1)
val sameMap = nonEmptyMap.ifEmpty { null }
println("nonEmptyMap === sameMap is ${nonEmptyMap === sameMap}") // true
//sampleEnd
}