React Hooks useCallback dependency infinite loop

Question

I'm currently fetching my data once when the component mounts, then whenever the user clicks a button. I want however to stop the button from fetching if a request is in progress, that's why I'm updating the isFetching state.

However, I need to add the isFetching to the useCallback dependency to remove the warning and if I do, an infinite fetch loop is triggered.

Here's my code:

import { useCallback, useEffect, useRef, useState } from 'react';

export const MyComponent = () => {
  const isMounted = useRef(true);
  const [isFetching, setIsFetching] = useState(false);
  
  const [data, setData] = useState(null);
  
  // Can also be called from the button click
  const getMyData = useCallback(() => {
    if (isFetching) return;
    setIsFetching(true);
    fetch('get/my/data')
      .then((res) => {
        if (isMounted.current) {
          setData(res.data);
        }
      })
      .catch((err) => {
        if (isMounted.current) {
          setData("Error fetching data");
        }
      })
      .finally(() => {
        if (isMounted.current) {
          setIsFetching(false);
        }
      });
  }, []); // isFetching dependency warning as is, if added then infinite loop

  useEffect(() => {
    isMounted.current = true;
    getMyData();
    return () => {
      isMounted.current = false;
    };
  }, [getMyData]);

  return (
    <div>
        <button onClick={getMyData}>Update data</button>
        <p>{data}</p>
    </div>
  );
};

I understand that there are multiple questions like this one, but I couldn't remove the warning or infinite loop while still checking if the component is mounted.

Here are some examples: example-1, example-2

Ori Drori · Accepted Answer · 2021-02-20 21:50:10Z

3

Convert isFetching to a ref, so it's value won't be a dependency of the function:

const { useCallback, useEffect, useRef, useState } = React;

const MyComponent = () => {
  const isMounted = useRef(true);
  const isFetching = useRef(false);
  
  const [data, setData] = useState([]);
  
  // Can also be called from the button click
  const getMyData = useCallback(() => {
    console.log('call');
    if (isFetching.current) return;
    isFetching.current = true;
    fetch('https://cat-fact.herokuapp.com/facts')
      .then(res => res.json())
      .then(res => {
        if (isMounted.current) {
          setData(res);
        }
      })
      .catch((err) => {
        if (isMounted.current) {
          setData("Error fetching data");
        }
      })
      .finally(() => {
        if (isMounted.current) {
          isFetching.current = false;
        }
      });
  }, []); // isFetching dependency warning as is, if added then infinite loop

  useEffect(() => {
    isMounted.current = true;
    getMyData();
    return () => {
      isMounted.current = false;
    };
  }, [getMyData]);

  return (
    <div>
      <button onClick={getMyData}>Update data</button>
      <ul>
      {
        data.map(({ _id, text }) => (
          <li key={_id}>{text}</li>
        ))
      }
      </ul>
    </div>
  );
};

ReactDOM.render(
  <MyComponent />,
  root
);

<script crossorigin src="https://unpkg.com/react@17/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@17/umd/react-dom.development.js"></script>

<div id="root"></div>

answered Feb 20, 2021 at 21:50

Ori Drori

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2 Comments

Annie Tan Over a year ago

How to use this ref to toggle loading indicator?

Ori Drori Over a year ago

Changing the ref won't cause a re-render, and the view won't change. You'll need to add another state (loading), and toggle it while you toggle the fetching ref.

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