Enum compared with sealed classes - devrath/KotlinAlchemy GitHub Wiki

Enum	SealedClasses
Enum classes represent a concrete set of values	sealed classes represent a concrete set of classes
They are perfect to represent a constant set of possible values	They are great to define a set of events or messages that might occur
The advantage of enum classes is that they can be serialized and deserialized out of the box. They have methods valueOf, values which are easy to iterate	The advantage of sealed classes is that they can hold instance-specific data

More differences

Number of Instances:

• Enum: An enum class in Kotlin is a special kind of sealed class that represents a set of distinct values. Each value is a singleton instance of the enum class. Enum instances are limited to the defined values within the enum class.
• Sealed Class: A sealed class can have multiple instances, each representing a different subtype. Sealed classes allow for a limited set of subclasses defined within the same file or module.

// Enum example
enum class Color {
    RED, GREEN, BLUE
}

// Sealed class example
sealed class Result
data class Success(val data: String) : Result()
data class Error(val message: String) : Result()

Extension:

• Enum: You cannot extend an enum class in Kotlin. Enum classes are final by default.
• Sealed Class: Sealed classes can be extended, but the subclasses must be defined in the same file or module where the sealed class is declared.

// Enum class (cannot be extended)
enum class Color { RED, GREEN, BLUE }

// Sealed class (can be extended)
sealed class Result
data class Success(val data: String) : Result()
data class Error(val message: String) : Result()

Properties and Methods:

• Enum: You can define properties and methods for each enum value, but they are shared among all instances.
• Sealed Class: Each subclass of a sealed class can have its own properties and methods. Sealed classes are more flexible in terms of allowing different behavior for each subtype.

// Enum with properties and methods
enum class Color(val rgb: Int) {
    RED(0xFF0000),
    GREEN(0x00FF00),
    BLUE(0x0000FF);

    fun toHexString(): String {
        return Integer.toHexString(rgb)
    }
}

// Sealed class with properties and methods
sealed class Result {
    data class Success(val data: String) : Result() {
        fun printData() {
            println(data)
        }
    }

    data class Error(val message: String) : Result() {
        fun printError() {
            println(message)
        }
    }
}