如何使用react hooks动态添加“ refs”？

Question

因此，我有一个数据数组，并且正在使用该数据生成组件列表。我想在每个生成的元素上都有一个引用来计算高度。我知道如何使用Class组件执行此操作，但是我想使用React Hooks进行操作。

这是一个说明我要做什么的示例：

import React, {useState, useCallback} from 'react'
const data = [
  {
    text: 'test1'
  },
  {
    text: 'test2'
  }
]
const Component = () => {
  const [height, setHeight] = useState(0);
  const measuredRef = useCallback(node => {
    if (node !== null) {
      setHeight(node.getBoundingClientRect().height);
    }
  }, []);

  return (
    <div>
      {
        data.map((item, index) => 
          <div ref={measuredRef} key={index}>
            {item.text}
          </div>
        )
      }
    </div>
  )
}

Answer 1

不确定我是否完全理解您的意图，但我认为您想要这样的东西：

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

const data = [
  {
    text: "test1"
  },
  {
    text: "test2"
  }
];

const Component = () => {
  const [heights, setHeights] = useState([]);
  const elementsRef = useRef(data.map(() => createRef()));

  useEffect(() => {
    const nextHeights = elementsRef.current.map(
      ref => ref.current.getBoundingClientRect().height
    );
    setHeights(nextHeights);
  }, []);

  return (
    <div>
      {data.map((item, index) => (
        <div ref={elementsRef.current[index]} key={index} className={`item item-${index}`}>
          {`${item.text} - height(${heights[index]})`}
        </div>
      ))}
    </div>
  );
};

const rootElement = document.getElementById("root");
ReactDOM.render(<Component />, rootElement);

.item {
  box-sizing: border-box;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid #ccc;
}

.item-0 {
  height: 25px;
}

.item-1 {
  height: 50px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.6/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.6/umd/react-dom.production.min.js"></script>
<div id="root"/>

Answer 2

我创建了一个npm小包，它公开了一个React Hook处理设置并动态获取引用的包，因为我经常遇到同样的问题。

npm i use-dynamic-refs

这是一个简单的例子。

import React, { useEffect } from 'react';
import useDynamicRefs from 'use-dynamic-refs';

const Example = () =>  {
  const foo = ['random_id_1', 'random_id_2'];
  const [getRef, setRef] =  useDynamicRefs();

  useEffect(() => {
    // Get ref for specific ID 
    const id = getRef('random_id_1');
    console.log(id)
  }, [])

    return ( 
      <>
        {/* Simple set ref. */}
        <span ref={setRef('random_id_3')}></span>

         {/*  Set refs dynamically in Array.map() */}
        { foo.map( eachId => (
          <div key={eachId} ref={setRef(eachId)}>Hello {eachId}</div>))}
      </>
    )
}

export default Example;