Why enums constrain values in Kotlin

Introduction

Enums help keep your program safe by only allowing certain fixed values. This stops mistakes where wrong or unexpected values might be used.

When you want to represent a small set of fixed options, like days of the week.

When you want to make sure a variable can only have certain allowed values.

When you want to improve code readability by naming specific states or choices.

When you want to avoid errors caused by using invalid values.

When you want to easily check or switch between known options.

Syntax

Kotlin

enum class Direction {
    NORTH, SOUTH, EAST, WEST
}

Enums define a type with a fixed set of named values.

Each value is called an enum constant.

Examples

This enum defines three colors you can use safely.

Kotlin

enum class Color {
    RED, GREEN, BLUE
}

This enum represents traffic light states, preventing invalid states.

Kotlin

enum class TrafficLight {
    RED, YELLOW, GREEN
}

Sample Program

This program uses an enum to limit size choices. The function prints a message based on the size chosen.

Kotlin

enum class Size {
    SMALL, MEDIUM, LARGE
}

fun describeSize(size: Size) {
    when (size) {
        Size.SMALL -> println("Small size selected")
        Size.MEDIUM -> println("Medium size selected")
        Size.LARGE -> println("Large size selected")
    }
}

fun main() {
    val mySize = Size.MEDIUM
    describeSize(mySize)
}

Important Notes

Enums prevent invalid values by restricting choices to predefined constants.

Using enums makes your code easier to read and maintain.

When you add new enum values, you can update your code to handle them explicitly.

Summary

Enums limit values to a fixed set, preventing errors.

They improve code clarity by naming specific options.

Enums help your program handle only valid, expected values.