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;

当前回答

我已经遇到过这个问题了。我的解决方案是:

在文件配置路由:

const routes = [
    { path: '/', title: '', component: Home },
    { path: '*', title: '', component: NotFound }
]

to:

const routes = [
    { path: '/', title: '', component: <Home /> },
    { path: '*', title: '', component: <NotFound /> }
]

其他回答

我已经遇到过这个问题了。我的解决方案是:

在文件配置路由:

const routes = [
    { path: '/', title: '', component: Home },
    { path: '*', title: '', component: NotFound }
]

to:

const routes = [
    { path: '/', title: '', component: <Home /> },
    { path: '*', title: '', component: <NotFound /> }
]

我所缺少的是我正在使用

import { Router, Route, browserHistory, IndexRoute } from 'react-router';

正确答案应该是:

import { BrowserRouter as Router, Route } from 'react-router-dom';

当然你需要添加npm包react-router-dom:

npm install react-router-dom@next --save
// @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>

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...
}

就我而言,VS Code让我失望了。

这是我的组件的层次结构:

<HomeScreen> =>  <ProductItemComponent> =>  <BadgeProductComponent>

我错误地导入了ProductItemComponent。事实上,这个组件以前在共享文件夹中,但后来它被移动到主文件夹中。但是当我将文件移动到另一个文件夹时,导入没有更新,保持不变:

../shared/components

同时,组件工作正常,VS Code没有突出显示错误。但是当我添加了一个新的BadgeProductComponent到ProductItemComponent,我有一个渲染错误,并认为问题是在新的BadgeProductComponent,因为当这个组件被删除,一切工作!

更重要的是,如果我通过热键到ProductItemComponent它有。/shared/components地址,然后VS Code重定向到Home文件夹的地址../ Home /components。

通常,检查所有组件级别上所有导入的正确性。