How to implement inheritance from a class declared as sealed?

In Kotlin, a class declared as sealed restricts inheritance to within the same file where it is declared. This means that inheriting from a sealed class is only possible in the same file where it is defined.

If a class is declared as sealed and is located in a different file, it cannot be inherited from.

Therefore, to implement inheritance from a sealed class, you need to:

• Be in the same file where the sealed class is declared.
• Declare subclasses within this file.

Example:

sealed class Result

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

If extendability outside the file is required, sealed class is not suitable; you should use a regular open class or interface.