What is a sealed class and what are its main advantages and features?

Sealed class — a special type of class in Kotlin (often used in Android development) that restricts the inheritance hierarchy. The main idea is that all subclasses of a sealed class must be declared in the same file as the sealed class itself.

Advantages and features:

• Allows the compiler to know the complete set of subclasses, which improves safety and convenience when working with when expressions — the compiler will check that all cases are handled.
• Simplifies modeling restricted hierarchies, such as states or events.
• Prevents creation of new subclasses outside the file, enhancing control over architecture.

Example:

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

fun handleResult(result: Result) {
    when(result) {
        is Result.Success -> println("Data: ${result.data}")
        is Result.Error -> println("Error: ${result.error.message}")
    }
}