react-native/Libraries/EventEmitter/mixInEventEmitter.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule mixInEventEmitter
 * @flow
 */
'use strict';

const EventEmitter = require('EventEmitter');
const EventEmitterWithHolding = require('EventEmitterWithHolding');
const EventHolder = require('EventHolder');

const invariant = require('fbjs/lib/invariant');
const keyOf = require('fbjs/lib/keyOf');

const TYPES_KEY = keyOf({__types: true});

/**
 * API to setup an object or constructor to be able to emit data events.
 *
 * @example
 * function Dog() { ...dog stuff... }
 * mixInEventEmitter(Dog, {bark: true});
 *
 * var puppy = new Dog();
 * puppy.addListener('bark', function (volume) {
 *   console.log('Puppy', this, 'barked at volume:', volume);
 * });
 * puppy.emit('bark', 'quiet');
 * // Puppy <puppy> barked at volume: quiet
 *
 *
 * // A "singleton" object may also be commissioned:
 *
 * var Singleton = {};
 * mixInEventEmitter(Singleton, {lonely: true});
 * Singleton.emit('lonely', true);
 */
function mixInEventEmitter(cls: Function | Object, types: Object) {
  invariant(types, 'Must supply set of valid event types');

  // If this is a constructor, write to the prototype, otherwise write to the
  // singleton object.
  const target = cls.prototype || cls;

  invariant(!target.__eventEmitter, 'An active emitter is already mixed in');

  const ctor = cls.constructor;
  if (ctor) {
    invariant(
      ctor === Object || ctor === Function,
      'Mix EventEmitter into a class, not an instance'
    );
  }

  // Keep track of the provided types, union the types if they already exist,
  // which allows for prototype subclasses to provide more types.
  if (target.hasOwnProperty(TYPES_KEY)) {
    Object.assign(target.__types, types);
  } else if (target.__types) {
    target.__types = Object.assign({}, target.__types, types);
  } else {
    target.__types = types;
  }
  Object.assign(target, EventEmitterMixin);
}

const EventEmitterMixin = {
  emit: function(eventType, a, b, c, d, e, _) {
    return this.__getEventEmitter().emit(eventType, a, b, c, d, e, _);
  },

  emitAndHold: function(eventType, a, b, c, d, e, _) {
    return this.__getEventEmitter().emitAndHold(eventType, a, b, c, d, e, _);
  },

  addListener: function(eventType, listener, context) {
    return this.__getEventEmitter().addListener(eventType, listener, context);
  },

  once: function(eventType, listener, context) {
    return this.__getEventEmitter().once(eventType, listener, context);
  },

  addRetroactiveListener: function(eventType, listener, context) {
    return this.__getEventEmitter().addRetroactiveListener(
      eventType,
      listener,
      context
    );
  },

  addListenerMap: function(listenerMap, context) {
    return this.__getEventEmitter().addListenerMap(listenerMap, context);
  },

  addRetroactiveListenerMap: function(listenerMap, context) {
    return this.__getEventEmitter().addListenerMap(listenerMap, context);
  },

  removeAllListeners: function() {
    this.__getEventEmitter().removeAllListeners();
  },

  removeCurrentListener: function() {
    this.__getEventEmitter().removeCurrentListener();
  },

  releaseHeldEventType: function(eventType) {
    this.__getEventEmitter().releaseHeldEventType(eventType);
  },

  __getEventEmitter: function() {
    if (!this.__eventEmitter) {
      let emitter = new EventEmitter();
      if (__DEV__) {
        const EventValidator = require('EventValidator');
        emitter = EventValidator.addValidation(emitter, this.__types);
      }

      const holder = new EventHolder();
      this.__eventEmitter = new EventEmitterWithHolding(emitter, holder);
    }
    return this.__eventEmitter;
  }
};

module.exports = mixInEventEmitter;