Clean up useEventEmitter

This commit is contained in:
Michael Telatynski 2019-10-19 16:48:39 +01:00
parent 02f8b18346
commit 4de0b3c177

View file

@ -1,3 +1,19 @@
/*
Copyright 2019 The Matrix.org Foundation C.I.C.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
import {useRef, useEffect} from "react"; import {useRef, useEffect} from "react";
// Hook to wrap event emitter on and removeListener in hook lifecycle // Hook to wrap event emitter on and removeListener in hook lifecycle
@ -6,19 +22,12 @@ export const useEventEmitter = (emitter, eventName, handler) => {
const savedHandler = useRef(); const savedHandler = useRef();
// Update ref.current value if handler changes. // Update ref.current value if handler changes.
// This allows our effect below to always get latest handler ...
// ... without us needing to pass it in effect deps array ...
// ... and potentially cause effect to re-run every render.
useEffect(() => { useEffect(() => {
savedHandler.current = handler; savedHandler.current = handler;
}, [handler]); }, [handler]);
useEffect( useEffect(
() => { () => {
// Make sure element supports on
const isSupported = emitter && emitter.on;
if (!isSupported) return;
// Create event listener that calls handler function stored in ref // Create event listener that calls handler function stored in ref
const eventListener = event => savedHandler.current(event); const eventListener = event => savedHandler.current(event);