javascript - 遇到两个拿着同把 key 的 child

Question

我真的是 React 和 redux 开发的新手。我有一个连接到容器的列表组件。我想更新滚动列表，但我得到:

Encountered two children with the same key

我的组件:

import React, { Component, PropTypes } from 'react'
import Track from './Track'
import styles from './TrackList.css'

const altImg = require('../images/sc.jpg');

export default class TrackList extends Component  {

  static propTypes = {
    tracks: PropTypes.arrayOf(PropTypes.shape({
    id: PropTypes.number.isRequired
      }).isRequired).isRequired,
    onTrackListScroll: PropTypes.func.isRequired
  }

 render() {
    const { tracks, onTrackListScroll } = this.props;
    return (
      <div>
      <ul className='tracks'
        onScroll={(e)=>{
          console.log('SCROLL!!',e)
          onTrackListScroll()
        }}>
        {tracks.map(track =>
          <Track
            key={track.id}
            {...track}
            //onClick={() => onTrackClick(track.id)}
            text={track.title}
            imgSrc={!track.artwork_url ? altImg : track.artwork_url}
          />
        )}
      </ul>
      </div>
    )

  }
}

reducer 更新状态是:

const toSearchResultOb = (tracks) => {
  return  {
    tracks: tracks
  }
}


case 'UPDATE_SEARCH_RESULT':
      return Object.assign({}, state, 
toSearchResultOb(state.tracks.concat(action.tracks)))

用 redux 更新组件 onScroll 的正确方法是什么？

Answer 1

您收到此错误是因为组件兄弟之间的键必须是唯一的。您的 tracks 数组中可能有重复的 track.id。

这是一个简单的解决方法:

{tracks.map(track, i =>
  <Track
    key={i}
    {...track}
    //onClick={() => onTrackClick(track.id)}
    text={track.title}
    imgSrc={!track.artwork_url ? altImg : track.artwork_url}
  />
)}

---

如果您在 MDN 上查看 map() 的文档，你会看到这个:

callback Function that produces an element of the new Array, taking three arguments:

• currentValue The current element being processed in the array.

• index The index of the current element being processed in the array.

所以在上面的例子中，i就是当前元素的索引。该索引在每次迭代时递增，这保证了 map() 中的唯一键。现在您不必担心 track.id 是什么。