kotlin-stdlib/kotlin.collections/mapNotNull

mapNotNull

inline fun <T, R : Any> Array<out T>.mapNotNull(transform: (T) -> R?): List<R>

Returns a list containing only the non-null results of applying the given transform function to each element in the original array.

Samples

import samples.*
import kotlin.test.*
fun main() { 
   //sampleStart 
   val strings: List<String> = listOf("12a", "45", "", "3")
val ints: List<Int> = strings.mapNotNull { it.toIntOrNull() }

assertPrints(ints, "[45, 3]")
assertPrints(ints.sum(), "48") 
   //sampleEnd
}

inline fun <T, R : Any> Iterable<T>.mapNotNull(transform: (T) -> R?): List<R>

Returns a list containing only the non-null results of applying the given transform function to each element in the original collection.

Samples

import samples.*
import kotlin.test.*
fun main() { 
   //sampleStart 
   val strings: List<String> = listOf("12a", "45", "", "3")
val ints: List<Int> = strings.mapNotNull { it.toIntOrNull() }

assertPrints(ints, "[45, 3]")
assertPrints(ints.sum(), "48") 
   //sampleEnd
}

inline fun <K, V, R : Any> Map<out K, V>.mapNotNull(transform: (Map.Entry<K, V>) -> R?): List<R>

Returns a list containing only the non-null results of applying the given transform function to each entry in the original map.

Samples

import samples.*
import kotlin.test.*
import java.util.*
fun main() { 
   //sampleStart 
   val map = mapOf("Alice" to 20, "Tom" to 13, "Bob" to 18)
val adults = map.mapNotNull { (name, age) -> name.takeIf { age >= 18 } }

assertPrints(adults, "[Alice, Bob]") 
   //sampleEnd
}