1

我目前在组件安装时获取我的数据一次，然后在用户单击按钮时获取。但是，如果请求正在进行中，我想停止获取按钮，这就是我更新isFetching状态的原因。

但是，我需要将 添加isFetching到useCallback依赖项以删除警告，如果这样做，则会触发无限获取循环。

这是我的代码：

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>
  );
};

我知道有多个像这样的问题，但我无法删除警告或无限循环，同时仍在检查组件是否已安装。

以下是一些示例：example-1，example-2

4

1 回答 1

2

转换isFetching为 ref，因此它的值不会是函数的依赖项：

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>

于 2021-02-20T21:50:10.943 回答