React.js - “本”甚至不确定结合

Question

我试图捕捉的onChange事件的输入，并呼吁的setState新值，但此后只要我在输入型我得到：

Uncaught TypeError: Cannot read property 'setState' of undefined 

即使我已经叫

this.handleChange.bind(this) 

在构造

index.js

import React from 'react' 
import * as ReactDOM from "react-dom"; 
import App from './App' 

ReactDOM.render(
    <App />, 
    document.getElementById('root') 
); 

App.js

import * as React from "react"; 
export default class App extends React.Component { 
    constructor(props) { 
     super(props) 
     this.handleChange.bind(this) 
     this.state = {contents: 'initialContent'} 
    } 


    handleChange(event) { 
     this.setState({contents: event.target.value}) 
    } 


    render() { 
     return (
      <div> 
       Contents = {this.state.contents} 
       <input type="text" onChange={this.handleChange}/> 
      </div> 
     ); 
    } 
} 

Answer 1

分配this.handleChange.bind(this)（绑定 - 返回新的参考起作用）至this.handleChange，因为this.handleChange不得不提及新函数返回.bind

。

constructor(props) { 
    super(props) 
    this.handleChange = this.handleChange.bind(this) 
    this.state = {contents: 'initialContent'} 
}