Enum

enum Permissions {
  case READ, WRITE, EXECUTE, NONE
}

val somePermission = Permissions.READ

Enum APIs

1. ordinal: the index of enum

   println(somePerission.ordinal) // 0. Because it's the first enum in Permissionss.
   

2. values: the list of all enums

   val allEnums = Permissions.values
   

3. valueOf: the Enum get from String

   val readEnum = Permission.valueOf("READ") // Permissions.READ