120 lines
3.2 KiB
JavaScript
120 lines
3.2 KiB
JavaScript
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @format
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* @flow
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*/
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'use strict';
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const invariant = require('fbjs/lib/invariant');
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class EventHolder {
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_heldEvents: Object;
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_currentEventKey: ?Object;
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constructor() {
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this._heldEvents = {};
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this._currentEventKey = null;
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}
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/**
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* Holds a given event for processing later.
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*
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* TODO: Annotate return type better. The structural type of the return here
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* is pretty obvious.
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*
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* @param {string} eventType - Name of the event to hold and later emit
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* @param {...*} Arbitrary arguments to be passed to each registered listener
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* @return {object} Token that can be used to release the held event
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*
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* @example
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*
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* holder.holdEvent({someEvent: 'abc'});
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*
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* holder.emitToHandler({
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* someEvent: function(data, event) {
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* console.log(data);
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* }
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* }); //logs 'abc'
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*
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*/
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holdEvent(eventType: string, ...args: any) {
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this._heldEvents[eventType] = this._heldEvents[eventType] || [];
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const eventsOfType = this._heldEvents[eventType];
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const key = {
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eventType: eventType,
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index: eventsOfType.length,
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};
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eventsOfType.push(args);
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return key;
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}
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/**
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* Emits the held events of the specified type to the given listener.
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*
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* @param {?string} eventType - Optional name of the events to replay
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* @param {function} listener - The listener to which to dispatch the event
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* @param {?object} context - Optional context object to use when invoking
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* the listener
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*/
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emitToListener(eventType: ?string, listener: Function, context: ?Object) {
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const eventsOfType = this._heldEvents[eventType];
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if (!eventsOfType) {
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return;
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}
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const origEventKey = this._currentEventKey;
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eventsOfType.forEach((/*?array*/ eventHeld, /*number*/ index) => {
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if (!eventHeld) {
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return;
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}
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this._currentEventKey = {
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eventType: eventType,
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index: index,
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};
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listener.apply(context, eventHeld);
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});
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this._currentEventKey = origEventKey;
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}
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/**
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* Provides an API that can be called during an eventing cycle to release
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* the last event that was invoked, so that it is no longer "held".
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*
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* If it is called when not inside of an emitting cycle it will throw.
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*
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* @throws {Error} When called not during an eventing cycle
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*/
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releaseCurrentEvent() {
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invariant(
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this._currentEventKey !== null,
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'Not in an emitting cycle; there is no current event',
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);
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this._currentEventKey && this.releaseEvent(this._currentEventKey);
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}
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/**
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* Releases the event corresponding to the handle that was returned when the
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* event was first held.
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*
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* @param {object} token - The token returned from holdEvent
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*/
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releaseEvent(token: Object) {
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delete this._heldEvents[token.eventType][token.index];
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}
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/**
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* Releases all events of a certain type.
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*
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* @param {string} type
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*/
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releaseEventType(type: string) {
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this._heldEvents[type] = [];
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}
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}
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module.exports = EventHolder;
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