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freeCodeCamp/guide/english/kotlin/extension-functions/index.md
2019-06-25 14:36:52 -05:00

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Extension Functions

Extension Functions

Kotlin supports extension functions & extension variables, which allow you to add new functionality to a class without modifying the class itself.

Basic Usage

Extension Function

fun String.containsSpaces(): Boolean {
  return contains(" ")
}

val myString = "Hello World"

print(myString.containsSpaces())

Output:

true

Extension Variable

val <T> List<T>.lastIndex: Int
    get() = size - 1

val myList = listOf(1,2,3,4,5)

print(myList.lastIndex)

Output:

4

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