How redirect to component when user login

Question

I'm trying to solve issue with redirection in react-router v4. I want to redirect to Index component if user is logged in and when load, reload show CodeClient component when user is logged out.

I never use react-router-dom, how can do it?

Somebody can explain me and show me with code how do it?

Here is my code:

import React, { Component } from 'react';

import './App.css';
import CodeClient from './components/Login/CodeClient';
import IndexComponent from './components/Index/IndexComponent';

class App extends Component {

    constructor(props) {
        super(props);
        this.state = { user: undefined, logged: false };
    }

    doParentCode = (user) => {
        // when user is different of undefined
        this.setState({ logged:true, user: user});
    }

    render() {

        return (
            <div className="Loggin">
                {
                    (!this.state.logged) ? <CodeClient parentCode={this.doParentCode} /> : <IndexComponent user={this.state.user}/>
                }
            </div>
        );
    }
}

export default App;