react-native/Libraries/Components/Subscribable.js

65 lines
1.9 KiB
JavaScript

/**
* Copyright (c) 2015-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @providesModule Subscribable
* @flow
*/
'use strict';
import type EventEmitter from 'EventEmitter';
/**
* Subscribable provides a mixin for safely subscribing a component to an
* eventEmitter
*
* This will be replaced with the observe interface that will be coming soon to
* React Core
*/
const Subscribable = {};
Subscribable.Mixin = {
UNSAFE_componentWillMount: function() {
this._subscribableSubscriptions = [];
},
componentWillUnmount: function() {
// This null check is a fix for a broken version of uglify-es. Should be deleted eventually
// https://github.com/facebook/react-native/issues/17348
this._subscribableSubscriptions && this._subscribableSubscriptions.forEach(
(subscription) => subscription.remove()
);
this._subscribableSubscriptions = null;
},
/**
* Special form of calling `addListener` that *guarantees* that a
* subscription *must* be tied to a component instance, and therefore will
* be cleaned up when the component is unmounted. It is impossible to create
* the subscription and pass it in - this method must be the one to create
* the subscription and therefore can guarantee it is retained in a way that
* will be cleaned up.
*
* @param {EventEmitter} eventEmitter emitter to subscribe to.
* @param {string} eventType Type of event to listen to.
* @param {function} listener Function to invoke when event occurs.
* @param {object} context Object to use as listener context.
*/
addListenerOn: function(
eventEmitter: EventEmitter,
eventType: string,
listener: Function,
context: Object
) {
this._subscribableSubscriptions.push(
eventEmitter.addListener(eventType, listener, context)
);
}
};
module.exports = Subscribable;