TypeError: Cannot read property

问题描述：

react组件中的方法获取state中的值时报错：TypeError: Cannot read property ‘state’ of undefined

解决办法：

方法一（在constructor中绑定this到函数）：this.funOne = this.funOne.bind(this);

import React , {Component} from 'react'; 

class Home extends Component {
    constructor(props){
        super(props); 

        this.state = {
            one: 'one'
        }

        this.funOne = this.funOne.bind(this); // 主要是这一行绑定this到函数funOne
    }

    funOne () {
        alert(this.state.one)
    }
    
    render () {
        return (
            <div className="Home">
                <button onClick={this.funOne}>funOne</button>
            </div>
        );
    }
}

export default Home;

方法二(使用箭头函数)：funOne = () => {}

import React , {Component} from 'react'; 

class Home extends Component {
    constructor(props){
        super(props); 

        this.state = {
            one: 'one'
        }
    }

    funOne = () => {
        alert(this.state.one)
    }
    
    render () {
        return (
            <div className="Home">
                <button onClick={this.funOne}>funOne</button>
            </div>
        );
    }
}

export default Home;

方法三（绑定方法的同时绑定this）：onClick={this.funOne.bind(this)}

import React , {Component} from 'react'; 

class Home extends Component {
    constructor(props){
        super(props); 

        this.state = {
            one: 'one'
        }
    }

    funOne () {
        alert(this.state.one)
    }
    
    render () {
        return (
            <div className="Home">
                <button onClick={this.funOne.bind(this)}>funOne</button>
            </div>
        );
    }
}

export default Home;