In what cases and where should you use sealed class declaration?

sealed class in Kotlin is used when you want to restrict the inheritance hierarchy to a specific set of subclasses. It is useful when all possible variants are known in advance and should be limited in one place.

Use cases include:

• Representing states in UI (State pattern)
• Describing operation results (success, error, loading)
• Handling events with known types

Example:

sealed class Result {
    data class Success(val data: String) : Result()
    data class Error(val error: Throwable) : Result()
    object Loading : Result()
}

Here, Result limits the variants of the result, making it easier to handle with when without an else branch.