Can't perform a React state update on an unmounted component
useEffect(() => {
let isMounted = true; // note mutable flag
someAsyncOperation().then(data => {
if (isMounted) setState(data); // add conditional check
})
return () => { isMounted = false }; // cleanup toggles value, if unmounted
}, []); // adjust dependencies to your needsreact warning can't perform a react state update on an unmounted component
componentWillUnmount() {
// fix Warning: Can't perform a React state update on an unmounted component
this.setState = (state,callback)=>{
return;
};
}Can't perform a React state update on an unmounted component
// custom Hook for automatic abortion on unmount or dependency change
// You might add onFailure for promise errors as well.
function useAsync(asyncFn, onSuccess) {
useEffect(() => {
let isActive = true;
asyncFn().then(data => {
if (isActive) onSuccess(data)
else console.log("aborted setState on unmounted component")
});
return () => {
isActive = false;
};
}, [asyncFn, onSuccess]);
}
const Child = () => {
const [state, setState] = useState("loading (4 sec)...");
useAsync(simulateFetchData, setState);
return <div>Child: {state}</div>;
};
const Parent = () => {
const [mounted, setMounted] = useState(true);
return (
<div>
Parent:
<button onClick={() => setMounted(!mounted)}>
{mounted ? "Unmount" : "Mount"} Child
</button>
{mounted && <Child />}
<p>
Unmount Child, while it is still loading. It won't set state later on,
so no error is triggered.
</p>
</div>
);
};
const simulateFetchData = () => new Promise(
resolve => setTimeout(() => resolve("data fetched"), 4000));
ReactDOM.render(<Parent />, document.getElementById("root"));Can't perform a React state update on an unmounted component
export default function MyComponent() {
const [loading, setLoading] = useState(false);
const [someData, setSomeData] = useState({});
let componentMounted = true; // (3) component is mounted
// ...
useEffect(() => {
setLoading(true);
someResponse = await doVeryLongRequest(); // it needs some time
// When request is finished:
if (componentMounted){ // (5) is component still mounted?
setSomeData(someResponse.data); // (1) write data to state
setLoading(false); // (2) write some value to state
}
return () => { // This code runs when component is unmounted
componentMounted = false; // (4) set it to false if we leave the page
}
}, []);
return (
<div className={loading ? "loading" : ""}>
{someData}
<a href="SOME_LOCAL_LINK">Go away from here!</a>
</div>
);
}Copyright © 2021 Codeinu
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