RouteConfiguration.md

Route Configuration

A route configuration is basically a set of instructions that tell a router how to try to match the URL and what code to run when it does. To illustrate some of the features available in your route config, let's expand on the simple app from the introduction.

import React from 'react'
import { render } from 'react-dom'
import { Router, Route, Link } from 'react-router'

const App = React.createClass({
  render() {
    return (
      <div>
        <h1>App</h1>
        <ul>
          <li><Link to="/about">About</Link></li>
          <li><Link to="/inbox">Inbox</Link></li>
        </ul>
        {this.props.children}
      </div>
    )
  }
})

const About = React.createClass({
  render() {
    return <h3>About</h3>
  }
})

const Inbox = React.createClass({
  render() {
    return (
      <div>
        <h2>Inbox</h2>
        {this.props.children || "Welcome to your Inbox"}
      </div>
    )
  }
})

const Message = React.createClass({
  render() {
    return <h3>Message {this.props.params.id}</h3>
  }
})

render((
  <Router>
    <Route path="/" component={App}>
      <Route path="about" component={About} />
      <Route path="inbox" component={Inbox}>
        <Route path="messages/:id" component={Message} />
      </Route>
    </Route>
  </Router>
), document.body)

As configured, this app knows how to render the following 4 URLs:

URL	Components
/	App
/about	App -> About
/inbox	App -> Inbox
/inbox/messages/:id	App -> Inbox -> Message

Adding an Index

Imagine we'd like to render another component inside of App when the URL is /. Currently, this.props.children inside of App's render method is undefined in this case. We can use an <IndexRoute> to specify a "default" page.

import { IndexRoute } from 'react-router'

const Dashboard = React.createClass({
  render() {
    return <div>Welcome to the app!</div>
  }
})

render((
  <Router>
    <Route path="/" component={App}>
      {/* Show the dashboard at / */}
      <IndexRoute component={Dashboard} />
      <Route path="about" component={About} />
      <Route path="inbox" component={Inbox}>
        <Route path="messages/:id" component={Message} />
      </Route>
    </Route>
  </Router>
), document.body)

Now, inside App's render method this.props.children will be a <Dashboard> element! This functionality is similar to Apache's DirectoryIndex or nginx's index directive, both of which allow you to specify a file such as index.html when the request URL matches a directory path.

Our sitemap now looks like this:

URL	Components
/	App -> Dashboard
/about	App -> About
/inbox	App -> Inbox
/inbox/messages/:id	App -> Inbox -> Message

Decoupling the UI from the URL

It would be nice if we could remove the /inbox segment from the /inbox/messages/:id URL pattern, but still render Message nested inside the App -> Inbox UI. Absolute paths let us do exactly that.

render((
  <Router>
    <Route path="/" component={App}>
      <IndexRoute component={Dashboard} />
      <Route path="about" component={About} />
      <Route path="inbox" component={Inbox} />

      {/* Use /messages/:id instead of /inbox/messages/:id */}
      <Route component={Inbox}>
        <Route path="messages/:id" component={Message} />
      </Route>
    </Route>
  </Router>
), document.body)

The ability to use absolute paths in deeply nested routes gives us complete control over what the URL looks like! We don't have to add more segments to the URL just to get nested UI.

We can now render the following URLs:

URL	Components
/	App -> Dashboard
/about	App -> About
/inbox	App -> Inbox
/messages/:id	App -> Inbox -> Message

Note: Absolute paths may not be used in route config that is dynamically loaded.

Preserving URLs

Wait a minute ... we just changed a URL! That's not cool. Now everyone who had a link to /inbox/messages/5 has a broken link. :(

Not to worry. We can use a <Redirect> to make sure that URL still works!

import { Redirect } from 'react-router'

render((
  <Router>
    <Route path="/" component={App}>
      <IndexRoute component={Dashboard} />
      <Route path="about" component={About} />

      <Route path="inbox" component={Inbox}>
        {/* Redirect /inbox/messages/:id to /messages/:id */}
        <Redirect from="messages/:id" to="/messages/:id" />
      </Route>

      <Route component={Inbox}>
        <Route path="messages/:id" component={Message} />
      </Route>
    </Route>
  </Router>
), document.body)

Now when someone clicks on that link to /inbox/messages/5 they'll automatically be redirected to /messages/5. 🙌

Enter and Leave Hooks

Routes may also define onEnter and onLeave hooks that are invoked once a transition has been confirmed. These hooks are useful for various things like requiring auth when a route is entered and saving stuff to persistent storage before a route unmounts.

During a transition, onLeave hooks run first on all routes we are leaving, starting with the leaf route on up to the first common ancestor route. Next, onEnter hooks run starting with the first parent route we're entering down to the leaf route.

Continuing with our example above, if a user clicked on a link to /about from /messages/5, the following hooks would run in this order:

• onLeave on the /messages/:id route
• onLeave on the /inbox route
• onEnter on the /about route

Configuration with Plain Routes

Since routes are usually nested, it's useful to use a concise nested syntax like JSX to describe their relationship to one another. However, you may also use an array of plain route objects if you prefer to avoid using JSX.

The <Redirect> configuration helper is not available when using plain routes, so you have to set up the redirect using the onEnter hook.

The route config we've discussed up to this point could also be specified like this:

const routes = {
  path: '/',
  component: App,
  indexRoute: { component: Dashboard },
  childRoutes: [
    { path: 'about', component: About },
    {
      path: 'inbox',
      component: Inbox,
      childRoutes: [{
        path: 'messages/:id',
        onEnter: ({ params }, replace) => replace(`/messages/${params.id}`)
      }]
    },
    {
      component: Inbox,
      childRoutes: [{
        path: 'messages/:id', component: Message
      }]
    }
  ]
}

render(<Router routes={routes} />, document.body)