react路由器4的具有公共布局的嵌套路由

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

// 公共布局组件
const Layout = ({ children }) => (
  <div>
    <header>这是公共头部</header>
    <nav>这是公共导航栏</nav>
    <main>{children}</main>
    <footer>这是公共底部</footer>
  </div>
);

// 子级路由组件
const Home = () => <h1>首页</h1>;
const About = () => <h1>关于我们</h1>;
const Contact = () => <h1>联系我们</h1>;

const App = () => (
  <Router>
    <Layout>
      <Switch>
        <Route exact path="/" component={Home} />
        <Route path="/about" component={About} />
        <Route path="/contact" component={Contact} />
      </Switch>
    </Layout>
  </Router>
);

export default App;