xstate/dist/declarations/src/assert.d.ts

Finite State Machines and Statecharts for the Modern Web.

import { EventDescriptor, EventObject, ExtractEvent } from "./types.js";
/**
 * Asserts that the given event object is of the specified type or types. Throws
 * an error if the event object is not of the specified types.
 *
 * @example
 *
 * ```ts
 * // ...
 * entry: ({ event }) => {
 *   assertEvent(event, 'doNothing');
 *   // event is { type: 'doNothing' }
 * },
 * // ...
 * exit: ({ event }) => {
 *   assertEvent(event, 'greet');
 *   // event is { type: 'greet'; message: string }
 *
 *   assertEvent(event, ['greet', 'notify']);
 *   // event is { type: 'greet'; message: string }
 *   // or { type: 'notify'; message: string; level: 'info' | 'error' }
 * },
 * ```
 */
export declare function assertEvent<TEvent extends EventObject, TAssertedDescriptor extends EventDescriptor<TEvent>>(event: TEvent, type: TAssertedDescriptor | readonly TAssertedDescriptor[]): asserts event is ExtractEvent<TEvent, TAssertedDescriptor>;