xstate/dist/declarations/src/actors/transition.d.ts

Finite State Machines and Statecharts for the Modern Web.

import { AnyActorSystem } from "../system.js";
import { ActorLogic, ActorRefFrom, ActorScope, EventObject, NonReducibleUnknown, Snapshot } from "../types.js";
export type TransitionSnapshot<TContext> = Snapshot<undefined> & {
    context: TContext;
};
export type TransitionActorLogic<TContext, TEvent extends EventObject, TInput extends NonReducibleUnknown, TEmitted extends EventObject = EventObject> = ActorLogic<TransitionSnapshot<TContext>, TEvent, TInput, AnyActorSystem, TEmitted>;
export type TransitionActorRef<TContext, TEvent extends EventObject> = ActorRefFrom<TransitionActorLogic<TransitionSnapshot<TContext>, TEvent, unknown>>;
/**
 * Returns actor logic given a transition function and its initial state.
 *
 * A “transition function” is a function that takes the current `state` and received `event` object as arguments, and returns the next state, similar to a reducer.
 *
 * Actors created from transition logic (“transition actors”) can:
 *
 * - Receive events
 * - Emit snapshots of its state
 *
 * The transition function’s `state` is used as its transition actor’s `context`.
 *
 * Note that the "state" for a transition function is provided by the initial state argument, and is not the same as the State object of an actor or a state within a machine configuration.
 *
 * @param transition The transition function used to describe the transition logic. It should return the next state given the current state and event. It receives the following arguments:
 * - `state` - the current state.
 * - `event` - the received event.
 * - `actorScope` - the actor scope object, with properties like `self` and `system`.
 * @param initialContext The initial state of the transition function, either an object representing the state, or a function which returns a state object. If a function, it will receive as its only argument an object with the following properties:
 * - `input` - the `input` provided to its parent transition actor.
 * - `self` - a reference to its parent transition actor.
 * @see {@link https://stately.ai/docs/input | Input docs} for more information about how input is passed
 * @returns Actor logic
 *
 * @example
 * ```ts
 * const transitionLogic = fromTransition(
 *   (state, event) => {
 *     if (event.type === 'increment') {
 *       return {
 *         ...state,
 *         count: state.count + 1,
 *       };
 *     }
 *     return state;
 *   },
 *   { count: 0 },
 * );
 *
 * const transitionActor = createActor(transitionLogic);
 * transitionActor.subscribe((snapshot) => {
 *   console.log(snapshot);
 * });
 * transitionActor.start();
 * // => {
 * //   status: 'active',
 * //   context: { count: 0 },
 * //   ...
 * // }
 *
 * transitionActor.send({ type: 'increment' });
 * // => {
 * //   status: 'active',
 * //   context: { count: 1 },
 * //   ...
 * // }
 * ```
 */
export declare function fromTransition<TContext, TEvent extends EventObject, TSystem extends AnyActorSystem, TInput extends NonReducibleUnknown, TEmitted extends EventObject = EventObject>(transition: (snapshot: TContext, event: TEvent, actorScope: ActorScope<TransitionSnapshot<TContext>, TEvent, TSystem>) => TContext, initialContext: TContext | (({ input, self }: {
    input: TInput;
    self: TransitionActorRef<TContext, TEvent>;
}) => TContext)): TransitionActorLogic<TContext, TEvent, TInput, TEmitted>;