React:绑定方法时无法读取未定义的属性'method()'

Question

嘿伙计们,我正在尝试渲染一个表中的反应,该表在单击状态时将行设置为选中状态.

单击该行时,我收到如下错误: Uncaught TypeError: Cannot read property 'setSelected' of undefined

有很多关于这个的问题,解决方案似乎是将这一行添加this.setSelected = this.setSelected.bind(this);到构造函数中,以便实际可以访问该函数.

我已经知道要做到这一点,正如你在下面看到的那样,我已经完成了它,它仍然给我错误.我完全难过了.

import React, { Component } from 'react';

class ShowsList extends Component {
  constructor(props) {
    super(props);
    this.state = {selected: {showID: null, i: null}};
    this.setSelected = this.setSelected.bind(this);
  }

  setSelected(event, showID, i) {
    this.setState({
      selected: {showID, i}
    });
    console.log(this.state.selected);
  }


  render() {
    return (
      <div className="shows-list">

      <table className="table">
  <thead>
    <tr>
      <th scope="col">ID</th>
      <th scope="col">Name</th>
      <th scope="col">Location</th>
      <th scope="col">Date</th>
      <th scope="col">Time</th>
    </tr>
  </thead>
  <tbody>
    {this.props.shows.map( function(show, i) {
      return (
        <tr
          key={i}
          onClick={(e) => {this.setSelected(e, show._id, i)}}>
          <td>{i+1}</td>
          <td>{show.eventName}</td>
          <td>{show.location}</td>
          <td>{show.date}</td>
          <td>{show.startTime}</td>
        </tr>);
    })}
  </tbody>
</table>

      </div>
    );
  }
}

export default ShowsList;

Answer 1

用function关键字声明的Javascript函数有自己的this上下文,所以thisinside里面this.props.shows.map( function(show, i)没有引用类.您可以使用箭头语法进行函数声明,这将松散地解析值this.更改

this.props.shows.map(function(show, i)

至

this.props.shows.map((show, i ) => {