Enums

Overview

Specs which inherit from sys::Enum define a closed enumerated range of string values. Enum specs are effectively sealed and cannot be extended.

Syntax

Enums are declared just like a dict spec with the enumerated range defined as slots between curly braces:

Suit: Enum {
  clubs
  diamonds
  hearts
  spades
}

The slot names define the range of valid string values for the enumerated type. The slots must not define a type - they are implied to be items for the parent enum type. The enum above specifies any value typed as Suit must be one of the following string values: "clubs", "diamonds", "hearts", or "spades".

In the case when the range of string values are not valid slot names, then define the string value via 'key' in the slot metadata:

Suit: Enum {
  clubs    <key:"Clubs">
  diamonds <key:"Diamonds">
  hearts   <key:"Hearts">
  spades   <key:"Spades">
}

The enum spec above has a valid range of "Clubs", "Diamonds", "Hearts", or "Spades". Note in this case the slot names such as "clubs" is not a valid string value for the enum.

You can also add arbitrary metadata to the enum and slots:

Suit: Enum <icon:"playing-card"> {
  clubs    <key:"Clubs",    color:"black">
  diamonds <key:"Diamonds", color:"red">
  hearts   <key:"Hearts",   color:"red">
  spades   <key:"Spades",   color:"black">
}