I am writing an application in React and was unable to avoid a super common pitfall, which is calling setState(...)
after componentWillUnmount(...)
.
I looked very carefully at my code and tried to put some guarding clauses in place, but the problem persisted and I am still observing the warning.
Therefore, I've got two questions:
Warning: Can't perform a React state update on an unmounted component.
This is a no-op, but it indicates a memory leak in your application.
To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount
method.
in TextLayerInternal (created by Context.Consumer)
in TextLayer (created by PageInternal) index.js:1446
d/console[e]
index.js:1446
warningWithoutStack
react-dom.development.js:520
warnAboutUpdateOnUnmounted
react-dom.development.js:18238
scheduleWork
react-dom.development.js:19684
enqueueSetState
react-dom.development.js:12936
./node_modules/react/cjs/react.development.js/Component.prototype.setState
react.development.js:356
_callee$
TextLayer.js:97
tryCatch
runtime.js:63
invoke
runtime.js:282
defineIteratorMethods/</prototype[method]
runtime.js:116
asyncGeneratorStep
asyncToGenerator.js:3
_throw
asyncToGenerator.js:29
Book.tsx
import { throttle } from 'lodash';
import * as React from 'react';
import { AutoWidthPdf } from '../shared/AutoWidthPdf';
import BookCommandPanel from '../shared/BookCommandPanel';
import BookTextPath from '../static/pdf/sde.pdf';
import './Book.css';
const DEFAULT_WIDTH = 140;
class Book extends React.Component {
setDivSizeThrottleable: () => void;
pdfWrapper: HTMLDivElement | null = null;
isComponentMounted: boolean = false;
state = {
hidden: true,
pdfWidth: DEFAULT_WIDTH,
};
constructor(props: any) {
super(props);
this.setDivSizeThrottleable = throttle(
() => {
if (this.isComponentMounted) {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
}
},
500,
);
}
componentDidMount = () => {
this.isComponentMounted = true;
this.setDivSizeThrottleable();
window.addEventListener("resize", this.setDivSizeThrottleable);
};
componentWillUnmount = () => {
this.isComponentMounted = false;
window.removeEventListener("resize", this.setDivSizeThrottleable);
};
render = () => (
<div className="Book">
{ this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }
<div className={this.getPdfContentContainerClassName()}>
<BookCommandPanel
bookTextPath={BookTextPath}
/>
<div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
<AutoWidthPdf
file={BookTextPath}
width={this.state.pdfWidth}
onLoadSuccess={(_: any) => this.onDocumentComplete()}
/>
</div>
<BookCommandPanel
bookTextPath={BookTextPath}
/>
</div>
</div>
);
getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';
onDocumentComplete = () => {
try {
this.setState({ hidden: false });
this.setDivSizeThrottleable();
} catch (caughtError) {
console.warn({ caughtError });
}
};
}
export default Book;
AutoWidthPdf.tsx
import * as React from 'react';
import { Document, Page, pdfjs } from 'react-pdf';
pdfjs.GlobalWorkerOptions.workerSrc = `//cdnjs.cloudflare.com/ajax/libs/pdf.js/${pdfjs.version}/pdf.worker.js`;
interface IProps {
file: string;
width: number;
onLoadSuccess: (pdf: any) => void;
}
export class AutoWidthPdf extends React.Component<IProps> {
render = () => (
<Document
file={this.props.file}
onLoadSuccess={(_: any) => this.props.onLoadSuccess(_)}
>
<Page
pageNumber={1}
width={this.props.width}
/>
</Document>
);
}
const DEFAULT_WIDTH = 140;
class Book extends React.Component {
setDivSizeThrottleable: ((() => void) & Cancelable) | undefined;
pdfWrapper: HTMLDivElement | null = null;
state = {
hidden: true,
pdfWidth: DEFAULT_WIDTH,
};
componentDidMount = () => {
this.setDivSizeThrottleable = throttle(
() => {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
},
500,
);
this.setDivSizeThrottleable();
window.addEventListener("resize", this.setDivSizeThrottleable);
};
componentWillUnmount = () => {
window.removeEventListener("resize", this.setDivSizeThrottleable!);
this.setDivSizeThrottleable!.cancel();
this.setDivSizeThrottleable = undefined;
};
render = () => (
<div className="Book">
{ this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }
<div className={this.getPdfContentContainerClassName()}>
<BookCommandPanel
BookTextPath={BookTextPath}
/>
<div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
<AutoWidthPdf
file={BookTextPath}
width={this.state.pdfWidth}
onLoadSuccess={(_: any) => this.onDocumentComplete()}
/>
</div>
<BookCommandPanel
BookTextPath={BookTextPath}
/>
</div>
</div>
);
getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';
onDocumentComplete = () => {
try {
this.setState({ hidden: false });
this.setDivSizeThrottleable!();
} catch (caughtError) {
console.warn({ caughtError });
}
};
}
export default Book;
This question is related to
javascript
reactjs
typescript
lodash
setstate
const handleClick = async (item: NavheadersType, index: number) => {
const newNavHeaders = [...navheaders];
if (item.url) {
await router.push(item.url); =>>>> line causing error (causing route to happen)
// router.push(item.url); =>>> coreect line
newNavHeaders.forEach((item) => (item.active = false));
newNavHeaders[index].active = true;
setnavheaders([...newNavHeaders]);
}
};
I had a similar problem and solved it :
I was automatically making the user logged-in by dispatching an action on redux ( placing authentication token on redux state )
and then I was trying to show a message with this.setState({succ_message: "...") in my component.
Component was looking empty with the same error on console : "unmounted component".."memory leak" etc.
After I read Walter's answer up in this thread
I've noticed that in the Routing table of my application , my component's route wasn't valid if user is logged-in :
{!this.props.user.token &&
<div>
<Route path="/register/:type" exact component={MyComp} />
</div>
}
I made the Route visible whether the token exists or not.
I had a similar issue thanks @ford04 helped me out.
However, another error occurred.
NB. I am using ReactJS hooks
ndex.js:1 Warning: Cannot update during an existing state transition (such as within `render`). Render methods should be a pure function of props and state.
What causes the error?
import {useHistory} from 'react-router-dom'
const History = useHistory()
if (true) {
history.push('/new-route');
}
return (
<>
<render component />
</>
)
This could not work because despite you are redirecting to new page all state and props are being manipulated on the dom or simply rendering to the previous page did not stop.
What solution I found
import {Redirect} from 'react-router-dom'
if (true) {
return <redirect to="/new-route" />
}
return (
<>
<render component />
</>
)
There is a hook that's fairly common called useIsMounted
that solves this problem (for functional components)...
import { useRef, useEffect } from 'react';
export function useIsMounted() {
const isMounted = useRef(false);
useEffect(() => {
isMounted.current = true;
return () => isMounted.current = false;
}, []);
return isMounted;
}
then in your functional component
function Book() {
const isMounted = useIsMounted();
...
useEffect(() => {
asyncOperation().then(data => {
if (isMounted.current) { setState(data); }
})
});
...
}
Functional component approach (Minimal Demo, Full Demo):
import React, { useState } from "react";
import { useAsyncEffect } from "use-async-effect2";
import cpFetch from "cp-fetch"; //cancellable c-promise fetch wrapper
export default function TestComponent(props) {
const [text, setText] = useState("");
useAsyncEffect(
function* () {
setText("fetching...");
const response = yield cpFetch(props.url);
const json = yield response.json();
setText(`Success: ${JSON.stringify(json)}`);
},
[props.url]
);
return <div>{text}</div>;
}
Class component (Live demo)
import { async, listen, cancel, timeout } from "c-promise2";
import cpFetch from "cp-fetch";
export class TestComponent extends React.Component {
state = {
text: ""
};
@timeout(5000)
@listen
@async
*componentDidMount() {
console.log("mounted");
const response = yield cpFetch(this.props.url);
this.setState({ text: `json: ${yield response.text()}` });
}
render() {
return <div>{this.state.text}</div>;
}
@cancel()
componentWillUnmount() {
console.log("unmounted");
}
}
I know that you're not using history, but in my case I was using the useHistory
hook from React Router DOM, which unmounts the component before the state is persisted in my React Context Provider.
To fix this problem I have used the hook withRouter
nesting the component, in my case export default withRouter(Login)
, and inside the component const Login = props => { ...; props.history.push("/dashboard"); ...
. I have also removed the other props.history.push
from the component, e.g, if(authorization.token) return props.history.push('/dashboard')
because this causes a loop, because the authorization
state.
An alternative to push a new item to history.
Based on @ford04 answer, here is the same encapsulated in a method :
import React, { FC, useState, useEffect, DependencyList } from 'react';
export function useEffectAsync( effectAsyncFun : ( isMounted: () => boolean ) => unknown, deps?: DependencyList ) {
useEffect( () => {
let isMounted = true;
const _unused = effectAsyncFun( () => isMounted );
return () => { isMounted = false; };
}, deps );
}
Usage:
const MyComponent : FC<{}> = (props) => {
const [ asyncProp , setAsyncProp ] = useState( '' ) ;
useEffectAsync( async ( isMounted ) =>
{
const someAsyncProp = await ... ;
if ( isMounted() )
setAsyncProp( someAsyncProp ) ;
});
return <div> ... ;
} ;
Edit: I just realized the warning is referencing a component called TextLayerInternal
. That's likely where your bug is. The rest of this is still relevant, but it might not fix your problem.
1) Getting the instance of a component for this warning is tough. It looks like there is some discussion to improve this in React but there currently is no easy way to do it. The reason it hasn't been built yet, I suspect, is likely because components are expected to be written in such a way that setState after unmount isn't possible no matter what the state of the component is. The problem, as far as the React team is concerned, is always in the Component code and not the Component instance, which is why you get the Component Type name.
That answer might be unsatisfactory, but I think I can fix your problem.
2) Lodashes throttled function has a cancel
method. Call cancel
in componentWillUnmount
and ditch the isComponentMounted
. Canceling is more "idiomatically" React than introducing a new property.
Depending on how you open your webpage, you may not be causing a mounting. Such as using a <Link/>
back to a page that was already mounted in the virtual DOM, so requiring data from a componentDidMount lifecycle is caught.
If above solutions dont work, try this and it works for me:
componentWillUnmount() {
// fix Warning: Can't perform a React state update on an unmounted component
this.setState = (state,callback)=>{
return;
};
}
try changing setDivSizeThrottleable
to
this.setDivSizeThrottleable = throttle(
() => {
if (this.isComponentMounted) {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
}
},
500,
{ leading: false, trailing: true }
);
The solution from @ford04 didn't worked to me and specially if you need to use the isMounted in multiple places (multiple useEffect for instance), it's recommended to useRef, as bellow:
"dependencies":
{
"react": "17.0.1",
}
"devDependencies": {
"typescript": "4.1.5",
}
export const SubscriptionsView: React.FC = () => {
const [data, setData] = useState<Subscription[]>();
const isMounted = React.useRef(true);
React.useEffect(() => {
if (isMounted.current) {
// fetch data
// setData (fetch result)
return () => {
isMounted.current = false;
};
}
}
});
Inspired by @ford04 answer I use this hook, which also takes callbacks for success, errors, finally and an abortFn:
export const useAsync = (
asyncFn,
onSuccess = false,
onError = false,
onFinally = false,
abortFn = false
) => {
useEffect(() => {
let isMounted = true;
const run = async () => {
try{
let data = await asyncFn()
if (isMounted && onSuccess) onSuccess(data)
} catch(error) {
if (isMounted && onError) onSuccess(error)
} finally {
if (isMounted && onFinally) onFinally()
}
}
run()
return () => {
if(abortFn) abortFn()
isMounted = false
};
}, [asyncFn, onSuccess])
}
If the asyncFn is doing some kind of fetch from back-end it often makes sense to abort it when the component is unmounted (not always though, sometimes if ie. you're loading some data into a store you might as well just want to finish it even if component is unmounted)
If you are fetching data from axios and the error still occurs, just wrap the setter inside the condition
let isRendered = useRef(false);
useEffect(() => {
isRendered = true;
axios
.get("/sample/api")
.then(res => {
if (isRendered) {
setState(res.data);
}
return null;
})
.catch(err => console.log(err));
return () => {
isRendered = false;
};
}, []);
To remove - Can't perform a React state update on an unmounted component warning, use componentDidMount method under a condition and make false that condition on componentWillUnmount method. For example : -
class Home extends Component {
_isMounted = false;
constructor(props) {
super(props);
this.state = {
news: [],
};
}
componentDidMount() {
this._isMounted = true;
ajaxVar
.get('https://domain')
.then(result => {
if (this._isMounted) {
this.setState({
news: result.data.hits,
});
}
});
}
componentWillUnmount() {
this._isMounted = false;
}
render() {
...
}
}
Inspired by the accepted answer by @ford04 I had even better approach dealing with it, instead of using useEffect
inside useAsync
create a new function that returns a callback for componentWillUnmount
:
function asyncRequest(asyncRequest, onSuccess, onError, onComplete) {
let isMounted=true
asyncRequest().then((data => isMounted ? onSuccess(data):null)).catch(onError).finally(onComplete)
return () => {isMounted=false}
}
...
useEffect(()=>{
return asyncRequest(()=>someAsyncTask(arg), response=> {
setSomeState(response)
},onError, onComplete)
},[])
Source: Stackoverflow.com