mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Tim Yung
d39643b9de
Summary: Rewrites `NativeEventEmitter` to not extend `EventEmitter` and to compose `RCTDeviceEventEmitter` instead of (mis)using its exported `sharedSubscriber` property. This makes it easier to reason about `NativeEventEmitter`. Also, the extraneous methods on `EventEmitter` are no longer inherited. Changelog: [General][Removed] - `NativeEventEmitter` no longer inherits from `EventEmitter`, so it no longer implements `removeListener` and `removeSubscription`. Instead, use the `remove()` method on the subscription object returned by `addListener`. Reviewed By: rubennorte Differential Revision: D26163562 fbshipit-source-id: c1aadb99bdefbaa36fece57ce74604e414f94d4d
100 lines
2.9 KiB
JavaScript
100 lines
2.9 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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* @flow strict-local
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* @format
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*/
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'use strict';
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import {
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type EventSubscription,
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type IEventEmitter,
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} from '../vendor/emitter/EventEmitter';
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import Platform from '../Utilities/Platform';
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import RCTDeviceEventEmitter from './RCTDeviceEventEmitter';
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import invariant from 'invariant';
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type NativeModule = $ReadOnly<{
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addListener: (eventType: string) => void,
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removeListeners: (count: number) => void,
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...
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}>;
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export type {EventSubscription};
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/**
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* `NativeEventEmitter` is intended for use by Native Modules to emit events to
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* JavaScript listeners. If a `NativeModule` is supplied to the constructor, it
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* will be notified (via `addListener` and `removeListeners`) when the listener
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* count changes to manage "native memory".
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*
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* Currently, all native events are fired via a global `RCTDeviceEventEmitter`.
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* This means event names must be globally unique, and it means that call sites
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* can theoretically listen to `RCTDeviceEventEmitter` (although discouraged).
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*/
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export default class NativeEventEmitter<TEventToArgsMap: {...}>
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implements IEventEmitter<TEventToArgsMap> {
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_nativeModule: ?NativeModule;
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constructor(nativeModule: ?NativeModule) {
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if (Platform.OS === 'ios') {
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invariant(
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nativeModule != null,
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'`new NativeEventEmitter()` requires a non-null argument.',
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);
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this._nativeModule = nativeModule;
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}
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}
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addListener<TEvent: $Keys<TEventToArgsMap>>(
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eventType: TEvent,
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listener: (...args: $ElementType<TEventToArgsMap, TEvent>) => mixed,
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context?: mixed,
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): EventSubscription {
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this._nativeModule?.addListener(eventType);
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let subscription: ?EventSubscription = RCTDeviceEventEmitter.addListener(
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eventType,
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listener,
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context,
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);
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return {
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remove: () => {
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if (subscription != null) {
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this._nativeModule?.removeListeners(1);
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subscription.remove();
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subscription = null;
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}
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},
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};
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}
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emit<TEvent: $Keys<TEventToArgsMap>>(
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eventType: TEvent,
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...args: $ElementType<TEventToArgsMap, TEvent>
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): void {
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// Generally, `RCTDeviceEventEmitter` is directly invoked. But this is
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// included for completeness.
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RCTDeviceEventEmitter.emit(eventType, ...args);
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}
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removeAllListeners<TEvent: $Keys<TEventToArgsMap>>(
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eventType?: ?TEvent,
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): void {
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invariant(
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eventType != null,
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'`NativeEventEmitter.removeAllListener()` requires a non-null argument.',
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);
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this._nativeModule?.removeListeners(this.listenerCount(eventType));
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RCTDeviceEventEmitter.removeAllListeners(eventType);
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}
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listenerCount<TEvent: $Keys<TEventToArgsMap>>(eventType: TEvent): number {
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return RCTDeviceEventEmitter.listenerCount(eventType);
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}
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}
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