Metadata

Each of the types above has an associated metadata function in M.metadata(), with some useful additions:

const {
  _,
  base,
  asIs,
  any,
  anyOf,
  maybe,
  withDefault,

  number,
  string,
  boolean,
  date,

  wrappedNumber,
  map,
  enumMap,
  stringMap,
  list,
  set
} = M.metadata()
_(Type, innerMetadata = [])

eg. _(Animal), _(M.List, [string()]), _(M.Map, [date(), number()])

To retrieve the metadata of Modélico types

base(Type)

Retrieve the metadata of standard models for extension. See JSON validation (Overridingthe reviver) for an example.

asIs(transform = identity)

Useful for simple transformations, eg.: asIs(x => 2 * x) to double numbers. It serves as base for primitive metadata and can be used to fix a value for debugging purposes, eg.: asIs(() => 0). It is up to you to implement toJSON() on the instance to reverse the transformation if you need to.

any()

Leaves the JSON input untouched (same as asIs(identity)).

anyOf([[metadata1, enumValue1], ..., [metadataN, enumValueN]] = [], field = 'type')

Useful to revive polymorphic JSON based on an enumerated field. The field defaults to type if not provided. See Reviving polymorphic JSON: (example 1) for an example. Note that anyOf does not return metadata, but a metadata-returning function. This is something you can use as well to revive some cases of polymorphic JSON.

number()

For native numbers

wrappedNumber()

Wraps numbers with ModelicoNumber to support -0, NaN and ±Infinity.

string()

For native numbers

boolean()

For native booleans

date()

To parse date-time strings, as defined by RFC 3339, section 5.6, eg. 1978-12-06T00:00:00.000Z.

map(keyMetadata = any(), valueMetadata = any())

eg. map(date(), string())

For ordered maps with arbitrary keys and values with JSON representation

[[<key1>, <value1>], [<key2>, <value2>]]
enumMap(enumMetadata, valueMetadata = any())

eg. enumMap(_(MyEnum), number())

For ordered maps with enum keys and arbitrary values with JSON representation

{"<enum1>": <value1>, "<enum2>": <value2>}
stringMap(valueMetadata = any())

eg. stringMap(date())

For ordered maps with string keys and arbitrary values with JSON representation

{"<string1>": <value1>, "<string2>": <value2>}
list(itemMetadata = any()), list([...itemMetadata])

eg. list(string()); tuples: list([number(), string()])

For arrays. It has support for tuples in the sense of fixed-length arrays with per-item metadata.

set(itemMetadata)

eg. set(number())

For ordered collections with no repeated values

maybe(metadata = any())

eg. maybe(string())

To declare a value as optional. Unless a value is a Maybe, it cannot be missing from the JSON or be null. See Optional / null values: Maybes for more details.

withDefault(metadata, default)

eg. withDefault(number(), 100)

To set a default if the value is null or missing. See Optional / null values: using with default for more details.

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