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lobito
Asked: 2020-09-25 12:41:40 +0800 CST 2020-09-25 12:41:40 +0800 CST

What is the difference between enum and sealed in Kotlin?

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What is the difference between enum(Enum Classes) and sealed(Sealed Classes). And when it is advisable to use them.

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

sealed class Direction {
    class NORTH
    class SOUTH
    class WEST
    class EAST
}
android

1 Answers

  1. Best Answer

    Sealed Classes are used to represent restricted class hierarchies, where a value can have one of a limited set of types, but cannot have any other type.

    Sealed Classes are, in a sense, an extension of enum classes : the set of values ​​for an enum type is also restricted, but each enum constant exists only as a single instance, whereas a subclass of a sealed class can have multiple instances. instances that can contain state.

    • In an enumeration, you can only have one object of each type.
    • In a sealed class you can have several objects of the same class.

    I present these examples so you can see the difference, as for your question, when is it advisable to use them?

    Actually the Sealed Classes (Sealed Classes) could be said to be an "Enum on steroids".

    enter image description here

    Enum :

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

    Sealed Class : A class with a specified number of subclasses

    sealed class Direction{
    class North(val value: Int) : Direction()
    class South(val value: Int) : Direction()
    class West(val value: Int) : Direction()
    class East(val value: Int) : Direction()

}

fun execute(direction: Direction)= when (direction) {
    is Direction.North -> direction.value + 0
    is Direction.East ->  direction.value + 90
    is Direction.South ->  direction.value + 180
    is Direction.West ->  direction.value + 270
}
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