content: import React from 'react';
  
  import Header from './component/Header';
  import Footer from './component/Footer';
  import TopicList from './component/TopicList';
  
  export default class  App extends React.Component {
    render() {
      return (
        <div className="container">
          <Header />
          {this.props.children ? this.props.children : <TopicList {...this.props} />}
          <Footer />
        </div>
      )
    }
  }
  