class Login extends React.Component {
    state = {
        redirectToReferrer: false
    };

    login = () => {
        fakeAuth.authenticate(() => {
            this.setState({ redirectToReferrer: true });
        });
    };

    render() {
        const { from } = this.props.location.state
            || { from: { pathname: "/" } };
        const { redirectToReferrer } = this.state;

        if (redirectToReferrer) {
            return <Redirect to={from} />;
        }

        return (
            <div>
                <p>You must log in to view the page at {from.pathname}</p>
                <button onClick={this.login}>Log in</button>
            </div>
        );
    }
}

class Login extends React.Component {
    constructor(){
        super();
        this.state = {
            redirectToReferrer: false
        };
    }

    ....

}

// BookContainer.js
import { Container } from 'unstated'
class BookContainer extends Container {
  state = {
    books: [],
    booksVisible: false
  }
  addBook = book => {
    const books = [...this.state.books, book]
    this.setState({ books })
  }
  toggleVisibility = () => {
    this.setState({
      booksVisible: !this.state.booksVisible
    })
  }
}
export {
  BookContainer
}