无效的挂钩调用.Hooks 只能在函数组件的主体内部调用 [英] Invalid hook call. Hooks can only be called inside of the body of a function component

问题描述

我想使用 React 在表格中显示一些记录，但我收到了这个错误:

I want to show some records in a table using React but I got this error:

无效的挂钩调用.Hooks 只能在 a 的主体内部调用功能组件.这可能发生在以下情况之一原因:

Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen for one of the following reasons:

1. 您的 React 和渲染器版本可能不匹配(例如 React DOM)
2. 您可能违反了 Hooks 规则
3. 您可能在同一个应用中拥有多个 React 副本，请参阅有关如何调试和解决这个问题.

import React, {
  Component
} 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,
  },
}));

class allowance extends Component {
  constructor() {
    super();
    this.state = {
      allowances: [],
    };

  }

  componentWillMount() {
    fetch('http://127.0.0.1:8000/allowances')
      .then(data => {

        return data.json();

      }).then(data => {

        this.setState({
          allowances: data
        });

        console.log("allowance state", this.state.allowances);
      })

  }



  render() {
    const classes = useStyles();
    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 > {
        this.state.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;

推荐答案

你只能从 React 函数中调用钩子.阅读更多这里.

You can only call hooks from React functions. Read more here.

只需将Allowance类组件转换为函数式组件即可.

Just convert the Allowance class component to a functional component.

工作 CodeSandbox 演示.

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

  useEffect(() => {
    fetch("http://127.0.0.1:8000/allowances")
      .then(data => {
        return data.json();
      })
      .then(data => {
        setAllowances(data);
      })
      .catch(err => {
        console.log(123123);
      });
  }, []);

  const classes = useStyles();
  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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