3.16. Kotlin enumerated class

3.16.1. Enumeration initialization #

Each enumeration is an instance of the enumeration class, which can be initialized:

enum class Color(val rgb: Int) { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) } 

The default name is the enumeration character name, and the value starts at 0. If you need to specify a value, you can use its constructor:

enum class Shape(value:Int){ ovel(100), rectangle(200) } 

Enumerations also support declaring their own anonymous classes and corresponding methods, as well as methods that override the base class. Suchas:

enum class ProtocolState { WAITING { override fun signal() = TALKING }, TALKING { override fun signal() = WAITING }; abstract fun signal(): ProtocolState } 

If the enumeration class defines any member, use a semicolon to separate theenumeration constant definition in the member definition

3.16.2. Use enumeration constants #

Kotlin enumeration class in has a compositing method that allows youto traverse the defined enumeration constant and get the enumeration constant by its name.

EnumClass.valueOf(value: String): EnumClass // Convert the specified name to an enumeration value. If the match is not successful, a IllegalArgumentException EnumClass.values(): Array<EnumClass> // Returns an enumeration value in the form of an array 

Get information about enumerations:

val name: String //Get Enumeration Name val ordinal: Int //Obtain the order in which enumeration values are defined in all enumeration arrays 

enum class Color{ RED,BLACK,BLUE,GREEN,WHITE } fun main(args: Array<String>) { var color:Color=Color.BLUE println(Color.values()) println(Color.valueOf("RED")) println(color.name) println(color.ordinal) } 

enum class RGB { RED, GREEN, BLUE } inline fun <reified T : Enum<T>> printAllValues() { print(enumValues<T>().joinToString { it.name }) } fun main(args: Array<String>) { printAllValues<RGB>() // Output RED, GREEN, BLUE }