What are the advantages and disadvantages of using sealed class in different project files?

Sealed class in Kotlin restricts inheritance: all subclasses must be declared in the same file as the sealed class itself, or in some cases within the same module.

Advantages of using sealed class in one file:

• Compactness and clarity: all variants of subclasses are visible immediately, which facilitates understanding and maintenance.
• The compiler can check the completeness of when-expressions, as all subclasses are known.

Disadvantages:

• Restriction on code organization: all subclasses must be in one file, which can lead to a large and cumbersome file.

Using sealed class in different files:

• In Kotlin 1.5+, subclasses of a sealed class can be declared in the same module but in different files if the sealed class is declared as sealed interface or with sealed and @JvmSealed.

Advantages:

• Better code organization, each subclass in a separate file.

Disadvantages:

• Loss of compactness, harder to see all variants of subclasses immediately.
• Possible difficulties with maintaining the completeness of when-expressions if the compiler does not see all subclasses.

The choice depends on the size of the project and organizational preferences.