Route

Route is a client + server routing library for Dart that helps make building single-page web apps and using HttpServer easier.

Installation

Add this package to your pubspec.yaml file:

dependencies:
  route: any

Then, run pub get to download and link in the package.

UrlPattern

Route is built around UrlPattern a class that matches, parses and produces URLs. A UrlPattern is similar to a regex, but constrained so that it is reversible, given a UrlPattern and a set of arguments you can produce the URL that when parsed returns those same arguments. This is important for keeping the URL space for your app flexible so that you can change a URL for a resource in one place and keep your app working.

Route lets you use the same URL patterns for client-side and server-side routing. Just define a library containing all your URLs.

As an example, consider a blog with a home page and an article page. The article URL has the form /article/1234. We want to show articles without reloading the page.

Example (urls.dart):

library urls;

import 'package:route/url_pattern.dart';

final homeUrl = new UrlPattern(r'/');
final articleUrl = new UrlPattern(r'/article/(\d+)');
final allUrls = [homeUrl, articleUrl];

Client Routing

On the client, there is a Router class that associates UrlPatterns to handlers. Given a URL, the router finds a pattern that matches, and invokes its handler. This is similar to HttpServer.addRequestHandler(matcher, handler) on the server. The handlers are then responsible for rendering the appropriate changes to the page.

The Router can listen to Window.onPopState events and invoke the correct handler so that the back button seamlessly works.

Example (client.dart):

library client;

import 'package:route/client.dart';

main() {
  var router = new Router()
      ..addHandler(homeUrl, showHome)
      ..addHandler(articleUrl, showArticle)
      ..listen();
}

void showHome(String path) {
  // nothing to parse from path, since there are no groups
}

void showArticle(String path) {
  var articleId = articleUrl.parse(req.path)[0];
  // show article page with loading indicator
  // load article from server, then render article
}

Server Routing

On the server, route gives you a utility function to match HttpRequests against UrlPatterns.

import 'urls.dart';
import 'package:route/server.dart';
import 'package:route/pattern.dart';

HttpServer.bind().then((server) {
  var router = new Router(server)
      ..filter(matchesAny(allUrls), authFilter)
      ..serve(homeUrl).listen(serverHome)
      ..serve(articleUrl, method: 'GET').listen(serveArticle)
      ..defaultStream.listen(serveNotFound);
});

Future<bool> authFilter(req) {
  return getUser(getUserIdCookie(req)).then((user) {
    if (user != null) return true;
    redirectToLoginPage(req);
    return false;
  });
}

serveArticle(req) {
  var articleId = articleUrl.parse(req.uri.path)[0];
  // retrieve article data and respond
}

Further Goals

• Integration with Polymer so that the changing of UI views can happen automatically.
• Handling different HTTP methods to help implement REST APIs.
• Automatic generation of REST URLs from a single URL pattern, similar to Ruby on Rails
• Helpers for nested views and key-value URL schemes common with complex apps.
• [Done] Server-side routing for the dart:io v2 HttpServer
• [Done] IE 9 support