Example of using a sealed class to describe different states

Demonstrate how a sealed class can be used to model a set of possible states of an object. Show the declaration of a sealed class and several of its subclasses, each representing a separate state, as well as an example of usage in a when (or similar) conditional operator without the need to add an else branch, since the compiler will check for exhaustiveness.

sealed class UiState {
    object Loading : UiState()
    data class Success(val data: List<String>) : UiState()
    data class Error(val cause: Throwable) : UiState()
}

fun render(state: UiState) {
    when (state) {
        is UiState.Loading -> println("Loading...")
        is UiState.Success -> println("Data: ${state.data}")
        is UiState.Error   -> println("Error: ${state.cause.message}")
    }
}

The example shows how a sealed class guarantees a complete set of options and simplifies working with different states in the code.