it must be a function, usually from React.PropTypes

Question

I want to pass string from Main to Header. It succeeds but warning. I'm a beginner of React so I can not figure out what it must be a function means.

Anyone knows how to solve this warning?

The warning is:

And my code is below:

Main.js

import React from 'react';  import Header from './Header'; import AppList from './AppList/AppList'; import Footer from './Footer';  const propTypes = {   mainInfo: React.PropTypes.shape({     title: React.PropTypes.string.isRequired,     apps: React.PropTypes.array.isRequired,   }), };  class Main extends React.Component {   static methodsAreOk() {     return true;   }    render() {     return (       <div>         <Header title={this.props.mainInfo.title} />         <AppList apps={this.props.mainInfo.apps} />         <Footer />       </div>     );   } }  Main.propTypes = propTypes;  export default Main; 

Header.js

import React from 'react';  const propTypes = {   title: React.PropTypes.string.isRequred, };  class Header extends React.Component {   static methodsAreOk() {     return true;   }    render() {     return (       <div className="header">         <h1>{this.props.title}</h1>       </div>     );   } }  Header.propTypes = propTypes;  export default Header; 

Answer 1

You have an error: React.PropTypes.string.isRequred. Spell isRequired correctly, and it should be ok.