Schema Keys

Key Type

It is very often that JSON documents, or cards, refer to other documents. We call these references keys. Technically keys are string values storing the id of another document.

To define the key type, use editor=key attribute:

[schema editor=key]
define Key atom;

And here’s the usage example:

record Card.CardCharacter[character]
{
    Key weapon;  // the reference to the weapon document
    ...
}

Restricting keys to a single category

The Key type defined above would accept the reference to any document at all. Most often this is not desirable, and you’d like to restrict accepted documents to a single category. This may be done using category attribute.

Example:

enum CardCategory
{
    character;
    weapon;
}

[schema root]
variant Card
{
    tag CardCategory category;
}

[schema editor=key]
define Key atom;

[schema category="weapon"]
define WeaponKey Key;

record Card.CardCharacter[character]
{
    WeaponKey weapon;
    ...
}

record Card.CardWeapon[weapon]
{
    ...
}

Restricting keys to several document types

Sometimes there’re multiple categories the key would accept. The possible approach is to use an interface marker and to accept only documents implementing a certain interface.

Example:

enum CardCategory
{
    weapon;
    gear;
    character;
}

[schema root]
variant Card
{
    tag CardCategory category;
}

[schema editor=key]
define Key atom;

interface IItem
{
    ...
}

[schema interface="IItem"]
define ItemKey Key;

record Card.CardWeapon[weapon] : IItem
{
    ...
}

record Card.CardGear[gear] : IItem
{
    ...
}

record Card.CardCharacter[character] // does not implement IItem
{
    list<ItemKey> default_inventory;
}