Why am I getting an \'Invalid Hook Call\' error in my React component and how can I fix it?-JS Tutorial-php.cn

Why am I getting an \'Invalid Hook Call\' error in my React component and how can I fix it?

Mary-Kate Olsen

Release： 2024-11-08 00:35:03

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Why am I getting an

Resolving "Invalid Hook Call" Error in React Component

React hooks provide a powerful way to interact with the component state, but they come with certain rules that must be followed. One common error that can occur is "Invalid hook call." This occurs when hooks are called outside the body of a function component.

Causes of the Error:

Mismatched React Versions: Ensure you have compatible versions of React and the renderer (e.g., React DOM).
Breaking Hook Rules: Hooks must be called in the same order during each render cycle and cannot be called inside conditional statements or loops.
Multiple Instances of React: Verify that there is only one copy of React in the application.

Troubleshooting the Issue:

In the provided code example, the issue can be traced to the componentWillMount method of the class component. React hooks are not supported in class components.

Solution:

To resolve this issue and use hooks, the component should be converted to a functional component. Here's the updated code:

import React, { useState, useEffect } from 'react';
import { makeStyles } from '@material-ui/core/styles';
import Table from '@material-ui/core/Table';
import TableBody from '@material-ui/core/TableBody';
import TableCell from '@material-ui/core/TableCell';
import TableHead from '@material-ui/core/TableHead';
import TableRow from '@material-ui/core/TableRow';
import Paper from '@material-ui/core/Paper';

const useStyles = makeStyles(theme => ({
  root: {
    width: '100%',
    marginTop: theme.spacing(3),
    overflowX: 'auto'
  },
  table: {
    minWidth: 650
  }
}));

const Allowance = () => {
  const [allowances, setAllowances] = useState([]);
  const classes = useStyles();

  useEffect(() => {
    fetch('http://127.0.0.1:8000/allowances')
      .then(data => data.json())
      .then(data => setAllowances(data));
  }, []);

  return (
    <Paper className={classes.root}>
      <Table className={classes.table}>
        <TableHead>
          <TableRow>
            <TableCell>Allow ID</TableCell>
            <TableCell align="right">Description</TableCell>
            <TableCell align="right">Allow Amount</TableCell>
            <TableCell align="right">AllowType</TableCell>
          </TableRow>
        </TableHead>
        <TableBody>
          {allowances.map(row => (
            <TableRow key={row.id}>
              <TableCell component="th" scope="row">{row.AllowID}</TableCell>
              <TableCell align="right">{row.AllowDesc}</TableCell>
              <TableCell align="right">{row.AllowAmt}</TableCell>
              <TableCell align="right">{row.AllowType}</TableCell>
            </TableRow>
          ))}
        </TableBody>
      </Table>
    </Paper>
  );
};

export default Allowance;

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Additional Note:

In some cases, the issue may also be caused by using an outdated version of react-scripts. Updating the version to the latest release could potentially resolve the problem.

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