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Throughout this lesson, you’ll learn:
- When to use enum classes in your project.
- How to define enum classes.
- How to use enum classes in code.
How Do You Declare Enum Class?
Enum classes provide a way to represent a fixed set of constants within a type-safe structure. They help you define a collection of related constants distinct from each other. You can declare an enum class using the enum class keyword followed by the name of the class:
enum class DayOfWeek {
MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY;
}
enum class ErrorType {
NOT_FOUND, INVALID_INPUT, SERVER_ERROR
}
enum class DropdownOption {
OPTION_BANANA, OPTION_APPLE, OPTION_GRAPE
}
fun main() {
val currentSelection = DropdownOption.OPTION_BANANA
println("Current selection: $currentSelection")
}
Reason of Using Enum Class
There are a few reasons to use enum classes.
fun createFruitBox(fruitBox: String): FruitBox {
return when (fruitBox) {
"Banana" -> Banana()
"Apple" -> Apple()
"Grape" -> Grape()
else -> throw IllegalArgumentException("Invalid fruit")
}
}
enum class Fruits {
BANANA,
APPLE,
GRAPE
}
fun createFruitBox(fruitBox: Fruits): FruitBox {
return when (fruitBox) {
Fruits.BANANA -> Banana()
Fruits.APPLE -> Apple()
Fruits.GRAPE -> Grape()
else -> throw IllegalArgumentException("Invalid fruit")
}
}