Enums & Sealed Interfaces: A Fixed Set of Choices

A fixed set of choices

A PawWalk user is an owner or a walker. Not both, not "ownerr" with a typo, not some surprise third thing. When a value can only be one of a known, fixed set of choices, Kotlin gives you the enum class.

You declare the choices as entries. A value of the type is exactly one entry: val status = BookingStatus.PENDING.