IntermediateOOP

Sealed Class

Model limited states with sealed classes.

kotlin
sealed class Result
data class Success(val data: String) : Result()
data class Error(val message: String) : Result()

fun describe(result: Result): String = when (result) {
    is Success -> "Got: ${result.data}"
    is Error -> "Error: ${result.message}"
}

fun main() {
    println(describe(Success("Loaded")))
    println(describe(Error("Not found")))
}

Output

Got: Loaded Error: Not found

Explanation

sealed classes restrict subclassing to the same file. when is exhaustive — no else needed when all subclasses are covered.

Sealed Class

Explanation

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