[英]Why does this react component, imported with System.import, not render?
我正在尝试使用webpack 2实现动态代码拆分并做出反应。 为了测试,我创建了一个异步导入代码的组件:
import React, { Component } from 'react'
export class Async extends Component {
constructor(props) {
super(props)
this.state = { component: <div>Loading</div> }
}
componentDidMount() {
System.import('../../about')
.then(component => this.setState({ component: component.About }))
.catch(error => this.setState({ component: <div>{error.message}</div> }))
}
render() {
return this.state.component
}
}
但是,当我安装它时,它返回以下错误:
Async.render(): A valid React element (or null) must be returned. You may have returned undefined, an array or some other invalid object.
将console.log(this.state.component)放入Async
的render函数中会导致以下结果:
那么,这里出了什么问题? 看来我正在获得有效的React组件,那么为什么会引发错误?
我认为您必须在{}
和<div>
包装this.state.component
,并且该错误是关于
您需要从组件中创建一个元素
class Async extends React.Component { constructor(props) { super(props); this.state = { component: React.createElement('div', {}, "loading") } } render() { return ( this.state.component ) } } ReactDOM.render(<Async/>, document.getElementById('app'))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.0.2/react.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.0.2/react-dom.min.js"></script> <div id="app"></div>
class Async extends React.Component {
constructor(props) {
super(props);
this.state = {
component: React.createElement('div', {}, "loading")
}
}
componentDidMount() {
System.import('../../about')
.then(component => this.setState({ component: React.createElement(component.About) }))
.catch(error => this.setState({ component: React.createElement('div', {}, error.message) }))
}
render() {
return (
this.state.component
)
}
}
当您实际上应该返回从该类创建的元素时,您将返回组件类。 他们不是一回事!
// Replace this:
render() {
return this.state.component
}
// With this:
render() {
return <this.state.component />
}
// Or this:
render() {
return React.createElement(this.state.component)
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.