TypeError: instance.render is not a function

2022-01-28 23:39 98阅读 0赞

1、错误描述

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95b3VoYWlkb25nLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70][]

2、错误原因

import React, {Component} from 'react';
    import {render} from 'react-dom';
    import Button from 'react-bootstrap/Button'
    
    class InputRead extends Component {
    	constructor() {
    		return { user: '' };
    	}
    	
    	inputChange(e) {
    		this.setState({user:e.target.value});
    	}
    	
    	clearAndFocus() {
    		this.setState({user:''},()=>{
    			this.refs.thisInput.focus();
    		})
    	}
    	
    	render() {
    		return (
    			<div>
    				<Button onClick={this.clearAndFocus.bind(this)}>
    					清空
    				</Button>
    				<input ref="thisInput" value={this.state.user} onChange={this.inputChange.bind(this)}/>
    			</div>
    		)
    	}
    }
    
    export default InputRead;

构造函数中不能使用return语句，否则以为构造函数中需要添加render()方法

3、解决办法

import React, {Component} from 'react';
    import {render} from 'react-dom';
    import Button from 'react-bootstrap/Button'
    
    class InputRead extends Component {
    	constructor(props) {
    		//return { user: '' };
    		super(props);
    		this.state = { user: '' };
    	}
    	
    	inputChange(e) {
    		this.setState({user:e.target.value});
    	}
    	
    	clearAndFocus() {
    		this.setState({user:''},()=>{
    			this.refs.thisInput.focus();
    		})
    	}
    	
    	render() {
    		return (
    			<div>
    				<Button onClick={this.clearAndFocus.bind(this)}>
    					清空
    				</Button>
    				<input ref="thisInput" value={this.state.user} onChange={this.inputChange.bind(this)}/>
    			</div>
    		)
    	}
    }
    
    export default InputRead;

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95b3VoYWlkb25nLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70]: /images/20220128/06959ce8f098484991ea7e50e7d6440d.png