Question

我在构造函数中绑定了this.handleChange = this.handleChange.bind(this);，但是仍然无法读取未定义的属性。

如何解决这个问题？

import React, { Component } from "react";
import moment from "moment";

class TimerConfig extends Component {
  constructor() {
    super();
    this.handleChange = this.handleChange.bind(this);
  }

  handChange(ev) {
    const newBaseTime = this.props.baseTime;

    if (ev.target.id === "hours")
      newBaseTime
        .subtract(newBaseTime.get("hour"), "hours")
        .add(parseInt(ev.target.value, 10), "hours");
    if (ev.target.id === "minutes")
      newBaseTime
        .subtract(newBaseTime.get("minutes"), "minutes")
        .add(parseInt(ev.target.value, 10), "minutes");
    if (ev.target.id === "seconds")
      newBaseTime
        .subtract(newBaseTime.get("seconds"), "seconds")
        .add(parseInt(ev.target.value, 10), "seconds");

    this.props.setBaseTime(newBaseTime);
  }

  render() {
    return (
      <div>
        <label for="hours">Hour</label>
        <input
          id="hours"
          type="number"
          defaultValue={this.props.baseTime.get("hours")}
          onChange={this.handleChange}
        />

        <label for="minutes">min</label>
        <input
          id="minutes"
          type="number"
          defaultValue={this.props.baseTime.get("minutes")}
          onChange={this.handleChange}
        />

        <label for="seconds">sec</label>
        <input
          id="seconds"
          type="number"
          defaultValue={this.props.baseTime.get("seconds")}
          onChange={this.handleChange}
        />
      </div>
    );
  }
}

export default TimerConfig;

Answer 1

您拼写了方法“ handChange”而不是“ handleChange”：）

Answer 2

要在bind中使用constructor时，需要将super与props一起使用

constructor(props){
  super(props);
  this.handleChange = this.handleChange.bind(this);
}

否则，您可以使用以下语法进行绑定：

handChange=(ev)=>{
//..
}

无法读取React.js中未定义的属性“绑定”

2 个答案: