variant/lib/lookup.d.ts

Variant types (a.k.a. Discriminated Unions) in TypeScript

import { Property, VariantsOfUnion } from './variant';
/**
 * An object that has the same keys as a variant but has arbitrary values for the data.
 * a.k.a. a lookup table.
 */
export declare type Lookup<T, U = any> = {
    [P in keyof T]: U;
};
/**
 * Process an unknown variant by comparing it to a provided lookup table and returning the proper result.
 * @param obj some object that extends `{[K]: string}`.
 * @param handler a lookup table going from the various keys of `obj`'s type to any.
 * @param typeKey the key used as the discriminant.
 */
export declare function lookup<T extends Property<K, string>, L extends Lookup<VariantsOfUnion<T, K>>, K extends string = 'type'>(obj: T, handler: L, typeKey?: K): L[keyof L];
/**
 * Process an unknown variant by comparing it to a provided lookup table and returning the proper result.
 * If the handler does not account for the case, returns undefined
 * @param obj some object that extends `{[K]: string}`.
 * @param handler a partial lookup table going from some keys of `obj`'s type to any.
 * @param typeKey the key used as the discriminant.
 */
export declare function partialLookup<T extends Property<K, string>, L extends Lookup<VariantsOfUnion<T, K>>, K extends string = 'type'>(obj: T, handler: Partial<L>, typeKey?: K): L | undefined;
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