RESS
A system for building mobile optimized Rails applications using semantic, media query-based device detection and server side component optimization.
Background
RESS is an extension of the devicejs library written by Boris Smus. It adds a back end for adapting server responses based on client side feature detection. RESS allows you to specify alternate versions of your website, along with media queries for which devices should be redirected to which version.
How it Works
HTML Annotations
When you register alternate mobile versions of your website, RESS adds annotations
to the <head> of your document that describe where these pages are located and
which devices should be redirected to them.
For example, a typical alternate version for a mobile site might include a tag like this:
<link rel="alternate" media="only screen and (max-width: 640px)" href="http://m.example.com/page-1" >The mobile version of the page would then have a link pointing back the canonical version:
<link rel="canonical" href="http://www.example.com/page-1" >These annotations conform to SEO best practices for mobile optimized websites as documented by Google.
Feature Detection
When a request comes into your site, the javascript included with ress will parse
all of the [rel="alternate"] links in your markup, and evalute their media queries
to determine if there is an alternate version available that matches the client.
If there is, the user is redirected to the url for that version.
Server Side Component Optimization
Ress allows you to customize how your Rails application responds to mobile requests in two ways:
- It adds controller and helper methods to detect which version of your site has been requested. This is useful for small tweeks in html or behaviour, eg:
<% if mobile_request? %>
<%= image_tag 'low-res.png' %>
<% else %>
<%= image_tag 'high-res.png' %>
<% end %>- It prepends a view path for each alternate version of your site, so that you can
override the templates or partials that are rendered for certain requests. For example if
you want to render a different html form for creating users on the mobile version of your
site you could create
app/mobile_views/users/_form.html.erband Ress would have Rails select that template overapp/views/users/_form.html.erbwhen a request comes in to the mobile version.
Installation
Add this line to your application's Gemfile:
gem 'ress'
And then execute:
$ bundle install
Run the generator:
$ rails g ress:install
Usage
Adding Alternate Versions
Alternate versions of an application are registered using the #add_alternate method in the
ress.rb initializer that is generated by the ress:install generator. The configurabe options
available are all documented in the comments of that file.
Version override
You can manually override the version detector javascript and allow mobile
clients to visit the canonical version of the app by passing in a the GET
url parameter force_canonical=1. This sets a session cookie in a before_filter
that stops the version detection scipt from redirecting users, so it only has to be
done once per session. Ress includes a helper / controller method force_canonical that returns
a link back to the canonical version of the current page with this query param appended.
For, example you may include something like this in your <footer> to let mobile users
access the canonical site.
<!-- Let mobile devices access the canonical site -->
<footer>
<% unless canonical_request? %>
<div>
You are currently viewing the mobile version of this site.
<%= link_to 'View the desktop version', force_canonical_url %>
</div>
<% end %>
</footer>Dependencies
There are a couple of Modernizr features that must be included in order for
Ress's javascript feature detection to function. If you are not already
using Modernizr in your application you can automatically include a build that
has been packaged with the gem by setting config.include_modernizr = true in
config/initializers/ress.rb. If you include your own build (recommended),
make sure that it includes "Touch Events" and "Media Queries", eg:
http://modernizr.com/download/#-touch-mq-teststyles-prefixes
Sessions and Cookies
In order to share sessions and cookies between the different subdomains used by the
alternate versions of your app, you need to configure the :domain option both in
the config/initializers/session_store.rb and when setting cookies. For more
information about how this works see this
Railscast.
Development
Because RESS uses subdomains, while developing alternate versions you cannot
load your site via localhost or an IP address. If you want to test on
the same machine you are running your rails app on, you can load it through
http://lvh.me or install pow and set up a .dev domain
for your app. If you need to test on a mobile device you might want to try
http://xip.io/.
Performance considerations
The javascript included by Ress does some checks and will use client-side
redirection to point users to the right version of your webapp. Client-side
redirection can have a performance overhead (though I haven't measured it).
If you find this is true, you can keep your DOM the same, still using the
SEO-friendly <link rel="alternate"> tags, but simply remove the
ress.js script and do your own server-side UA-based redirection.
Browser support
The feature detection javascript should work in all browsers that support
document.querySelectorAll. Notably, this excludes IE7. If you want it
to work in IE7 and below, please include a polyfill.
Contributing
Given how many browsers and devices we have these days, there are bound to be bugs. If you find them, please report them and (ideally) fix them in a pull request.
- Fork it
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create new Pull Request
Resources
Ress is the compilation of a few different ideas packaged up for Ruby on Rails. You may want to look at the following articles for more info:
- devicejs - a javascript library for client side feature direction and the main inspiration for this gem. Boris has also provided a good write up about it on http://www.html5rocks.com/
- Building Smartphone-Optimized Websites - Google's recommendations and best practices for building Mobile Optimized web apps
- RESS: Responsive Design + Server Side Components - an article by Luke Wroblewski about combining Responsive Design and Server Side Components (the inspiration for the name RESS).