Enums are predefined compile-time constants that contain predefined constants.

Kotlin Enum Syntax and Example

An Enum class is a custom class defined by a group of constants.

CONSTANTS can be of any type with optional values, and these constants are separated by commas.

Each constant is of the Data type Enum_Class.

enum class Enum_Class{
  CONSTANT1[(Optionalvalue)],
  CONSTANT2[(Optionalvalue)],
  CONSTANT3[(Optionalvalue)],
  ....
  CONSTANTN[(Optionalvalue)],
}

Here is an example


enum class Weekend {
    SATURDAY, SUNDAY
}

Kotlin Enum with Int values initialization

The enum class contains constants initialized with values.

class declaration must contain a datatype parameter to define the value.

Below Kotlin class is declared with an int value and each constant is initialized with an int value.

enum class Weekend(val value: Int) {
    SATURDAY(0), SUNDAY(1)
}

## Kotlin Enum with String values initialization

Enum class types c


enum class Status(val type: String) {
    INVITED("invite"),
    ACTIVATED("active"),
    DELETED("delete"),

}

How to get String or Int value from an Enum?

Create a function, take the Enum class object, and return the String value of it.


fun getStringValue(status: Status): String {
  return status.str;

}

getStringValue() function is called inside the main function by passing an Enum constant.

Here is an example


fun main() {
    println(getStringValue(Status.INVITED))

}

enum class Status(val str: String) {
    INVITED("invite"),
    ACTIVATED("active"),
    DELETED("delete"),

}

fun getStringValue(status: Status): String {

  return status.str;

}

Kotlin Enum Class iterate values

There are multiple ways, can iterate Enum class constants.

Enum class has a ‘values()’ method that returns an array of constants.

import java.util.Arrays
enum class Weekend {
    SATURDAY, SUNDAY

}

fun main() {
    val weekends = Weekend.values()
    println(weekends.contentToString())

}

Another way is enumValues<Enum> which returns an array of constants.

import java.util.Arrays
enum class Weekend {
    SATURDAY, SUNDAY
}

fun main() {
    val weekends = enumValues<Weekend>()
    println(weekends.contentToString())

}

Another way Using for Loop

The values() function returns an array, uses the forEach loop with a lambda expression to loop the element, and prints it.

Simplified, using method references to call the println function

import java.util.Arrays

enum class Weekend {
    SATURDAY, SUNDAY
}

fun main() {
    val weekends = Weekend.values()
    // lambda expression forEach
    Weekend.values().forEach { println(it) }
    // method reference
    Weekend.values().forEach(::println)

}