"Can't perform a React state update on an unmounted component" Code Answer's

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 a useEffect cleanup function.

By Fine Flamingo on Jun 28, 2020

## Description

This issue usually happens when you're trying to apply state 
changes to a component that does not exists anymore.

Often happens when the component gets removed from a tree
while there is a promise running in one of it's lifecycles.

The best way to fix it is to make sure that if there is any
promises in your component lifecycle, it should abort those
once the component gets unmounted from the tree.

Here is an interesting article that gives you a reproduction of this
error together with one type of solution https://www.debuggr.io/react-update-unmounted-component/

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react warning can't perform a react state update on an unmounted component

By Dull Donkey on Oct 15, 2020

componentWillUnmount() {
    // fix Warning: Can't perform a React state update on an unmounted component
    this.setState = (state,callback)=>{
        return;
    };
}

Source: stackoverflow.com

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Can't perform a React state update on an unmounted component

By Fierce Flamingo on May 25, 2021

useEffect(() => {
    const source = axios.CancelToken.source()

    const fetchUsers = async () => {
        try {
            await Axios.get('/users', {
                cancelToken: source.token,
            })
            // ...
        } catch (error) {
            if (Axios.isCancel(error)) {
            } else {
                throw error
            }
        }
    }

    fetchData()

    return () => {
        source.cancel()
    }
}, [])

Source: dev.to

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Can't perform a React state update on an unmounted component

By Xenophobic Xenomorph on Jun 16, 2021

// 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"));

Source: stackoverflow.com

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