runtypesOptionalExample.ts

import {
  Boolean,
  Number,
  String,
  Literal,
  Array,
  Tuple,
  Record,
  Union,
  Null,
  Partial,
  Static,
} from "runtypes";

const Vector = Tuple(Number, Number, Number);

const Planet = Record({
  type: Literal('planet'),
  location: Vector,
  mass: Number,
  population: Number,
  habitable: Boolean,
});

const Rank = Union(
  Literal('captain'),
  Literal('first mate'),
  Literal('officer'),
  Literal('ensign'),
);

const CrewMember = Record({
  name: String,
  age: Number,
  rank: Rank,
  home: Planet,
});

const Ship = Record({
  type: Literal('ship'),
  location: Vector,
  mass: Number,
  name: String,
  crew: Array(CrewMember),
});

const RegisteredShip = Ship.And(Record({
  // All registered ships must have this flag
  isRegistered: Literal(true),
})).And(Partial({
  // We may or may not know the ship's classification
  shipClass: Union(Literal('military'), Literal('civilian')),

  // We may not know the ship's rank (may be undefined as part of a "Partial"),
  // we may also know that a civilian ship doesn't have a rank (null)
  rank: Rank.Or(Null),
}));

const MilitaryShip = Ship.And(Record({
  shipClass: Literal('military'),
  lastDeployedTimestamp: Number.Or(Null),
}));

var ussSpacejam: Static<typeof RegisteredShip> = {
  type: "ship",
  location: [0.5, 0.5, 0.5],
  mass: 2_000_000,
  name: "USS Spacejam",
  crew: [],
  isRegistered: true,

  // e.g. this works
  rank: undefined
};

console.warn('isRegistered', RegisteredShip.guard(ussSpacejam)); // true
console.warn('isMilitary', MilitaryShip.guard(ussSpacejam)); // false