尝试得到react-router (v4.0.0)和react-hot loader (3.0.0-beta.6)很好地发挥，但在浏览器控制台得到以下错误:
Warning: React.createElement: type is invalid -- expected a string
(for built-in components) or a class/function (for composite
components) but got: undefined. You likely forgot to export your
component from the file it's defined in.
index.js:
import React from 'react';
import ReactDom from 'react-dom';
import routes from './routes.js';
require('jquery');
import 'bootstrap/dist/css/bootstrap.min.css';
import 'bootstrap/dist/js/bootstrap.min.js';
import './css/main.css';
const renderApp = (appRoutes) => {
ReactDom.render(appRoutes, document.getElementById('root'));
};
renderApp( routes() );
routes.js:
import React from 'react';
import { AppContainer } from 'react-hot-loader';
import { Router, Route, browserHistory, IndexRoute } from 'react-router';
import store from './store/store.js';
import { Provider } from 'react-redux';
import App from './containers/App.jsx';
import Products from './containers/shop/Products.jsx';
import Basket from './containers/shop/Basket.jsx';
const routes = () => (
<AppContainer>
<Provider store={store}>
<Router history={browserHistory}>
<Route path="/" component={App}>
<IndexRoute component={Products} />
<Route path="/basket" component={Basket} />
</Route>
</Router>
</Provider>
</AppContainer>
);
export default routes;
所以我遇到了这个问题，我用一种奇怪的方式解决了它。我想我应该把它扔了，以防其他人遇到它，变得绝望。
我有一个有条件地呈现react元素，它只在对象状态大于零时才会呈现。在呈现函数中-当三元运算符被证明为真时，我收到了这篇文章所涉及的错误。我使用了一个<React。片段>在我的渲染函数-这是我通常分组子的方式，而不是更新的方式与更新的短语法(<>和</>)。
However, when I changed the <React.Fragment> to the short syntax - the react element rendered correctly and the error stopped appearing. I took a look at Facebooks React-Fragment documentation, and I don't see any reason on there to believe there is a dramatic difference between the two that would cause this. Regardless, below are two simplified snippets of code for your review. The first one demonstrates the code that was yielding the error, and the second one demonstrates the code that fixed the issue. At the bottom is the render function of the component itself.
希望有人觉得这有帮助。
代码示例1 -错误
有条件渲染的React元素
renderTimeFields = () => {
return (
<React.Fragment>
<div className="align-left">
<div className="input-row">
<label>Date: </label>
<input type="date" className="date" name="date" min={new Date().toISOString().split('T')[0]} required/>
</div>
</div>
<div className="align-left sendOn-row">
<div className="input-row">
<label>Time: </label>
<input type="time" className="time" name="time" required/>
</div>
</div>
</React.Fragment>
);
}
代码示例2 -无错误
有条件渲染的React元素
renderTimeFields = () => {
return (
<>
<div className="align-left">
<div className="input-row">
<label>Date: </label>
<input type="date" className="date" name="date" min={new Date().toISOString().split('T')[0]} required/>
</div>
</div>
<div className="align-left sendOn-row">
<div className="input-row">
<label>Time: </label>
<input type="time" className="time" name="time" required/>
</div>
</div>
</>
);
}
在组件中呈现函数
render() {
<form>
...
{emailsInActiveScript > 1 ? this.renderTimeFields() : null}
</form>
etc...
}
大多数情况下，这是由于不正确的导出/导入。
常见错误:
// File: LeComponent.js
export class LeComponent extends React.Component { ... }
// File: App.js
import LeComponent from './LeComponent';
可能的选项:
// File: LeComponent.js
export default class LeComponent extends React.Component { ... }
// File: App.js
import LeComponent from './LeComponent';
有几种方法可能是错误的，但这种错误是由于导入/导出不匹配造成的，每次都是如此。
Edit
通常情况下，您应该得到一个堆栈跟踪，它指示故障发生的大致位置。这通常跟在你最初问题的信息之后。
如果没有显示，可能需要调查原因(可能是您遗漏了一个构建设置)。无论如何，如果它没有显示，唯一的操作方法是缩小导出/导入失败的地方。
遗憾的是，在没有stacktrace的情况下，唯一的方法是手动删除每个模块/子模块，直到您不再得到错误，然后再从堆栈中返回。
编辑2
通过注释，这确实是一个导入问题，特别是导入一个不存在的模块
// @flow
import React from 'react';
import { styleLocal } from './styles';
import {
View,
Text,
TextInput,
Image,
} from 'react-native';
import { TouchableOpacity } from 'react-native-gesture-handler';
export default React.forwardRef((props, ref) => {
const { onSeachClick, onChangeTextSearch , ...otherProps } = props;
return (
<View style={styleLocal.sectionStyle}>
<TouchableOpacity onPress={onSeachClick}>
<Image
source={require('../../assets/imgs/search.png')}
style={styleLocal.imageStyle} />
</TouchableOpacity>
<TextInput
style={{ flex: 1, fontSize: 18 }}
placeholder="Search Here"
underlineColorAndroid="transparent"
onChangeText={(text) => { onChangeTextSearch(text) }}
/>
</View>
);
});
import IGPSSearch from '../../components/IGPSSearch';
<Search onSeachClick={onSeachClick} onChangeTextSearch= {onChangeTextSearch}> </Search>
