ChoiceSchemaclass

Schema that validates a value against a fixed set of allowed string choices.

• The input must be one of the keys in options, otherwise it is rejected.
• Each choice has a human-readable title used by format().

Validates that a value is one of a known set of options — designed to power a <select> field in HTML. The validated type is the union of the option keys.

CHOICE is the sugar factory that builds a ChoiceSchema from either an array of strings (keys and labels are the same) or an object (keys are the validated values, object values are display labels).

Usage

import { CHOICE } from "shelving/schema";

// Array form — keys and labels are the same.
const STATUS = CHOICE(["draft", "published", "archived"] as const);
STATUS.validate("published"); // "published"
STATUS.validate("deleted");   // throws "Unknown value"

// Object form — keys are validated values, object values are display labels.
const Priority = CHOICE({ low: "Low priority", high: "High priority" });

ChoiceSchema is iterable and exposes .keys() and .entries() for building select menus. It does not implicitly default to the first option; pass value if you want a preselected choice.

Input control

input tells a form UI which control to show. It defaults from the number of options: "radio" for 8 or fewer, "select" for more. Set it to always use one control:

import { ChoiceSchema } from "shelving/schema";

const UNIT = new ChoiceSchema({ options: ["kg", "g", "lb"], input: "select" }); // Always a <select>.
const SIZE = new ChoiceSchema({ options: ["s", "m", "l", "xl"], input: "radio" }); // Always radios.