Rails 3 Routing with Rack

Sun Feb 07 05:56:12 -0800 2010

You probably all have heard that “Rails lets you route to Rack applications directly” and thought “Oh really?” well… bet you didn’t think it would be this simple.

Rails 3 really opens up a whole new world of pluggable awesomeness. This post expects you have already installed Rails 3 —prerelease, if not, follow the instructions in the Release Notes

The goal here is to make a Sinatra app run inside of Rails, taking routes it needs directly using the new Rails routing features.

Code is better at talking than me, so first make a new app:

$ rails app

Let rails do its thing. Then we want to make a simple Sinatra app, let’s make it marginally useful and have it hit Twitter.

Make a directory lib/twitter and in there make a new file called twitter_app.rb, inside of it put:

class TwitterApp < Sinatra::Base
  set :root, File.dirname(__FILE__)

  get '/twitter' do
    @user = 'raasdnil'
    t = Twitter::Search.new(@user).fetch
    @tweets = t.results
    erb :twitter
  end

end

This is a basic Sinatra app, it first sets its root directory to be the directory of the current file (needed because using the Rails root will not work) and then responds to one url /twitter that uses the Twitter gem to do the heavy lifting on searching for all the tweets by some weirdo (me).

It then assigns all the tweets to an instance variable and renders the template twitter.erb.

We have to make this template, so create another folder lib/twitter/views and make a file in there called twitter.erb and put in the following:

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Tweets mentioning <%= @user %></title>
  </head>
  <style type="text/css" media="screen">
    div.tweet { border: 1px solid gray;
                height: 50px;
                width: 600px;
                padding: 5px;
                margin-bottom: 10px; }
    img.icon { float: left; padding-right: 10px; }
    div.text { font-family: verdana, sans-serif; }
    div.<%= @user %> { background: #F4F4FF; }
  </style>
  <body>
    <% @tweets.each do |tweet| %>
    <div class="tweet  <%= tweet.from_user %>" id="<%= tweet.id %>">
      <img class="icon" src="<%= tweet.profile_image_url %>" />
      <div class="text" >
        <%= tweet.text %>
      </div>
    </div>
    <% end %>
  </body>
</html>

OK, our Sinatra app is ready to fire. Now hooking it up is simple.

First, we need to make sure we require the needed gems, so open up your Gemfile in Rails root and add the following:

## Bundle the gems you use:
gem "sinatra", "0.9.2"
gem "twitter", "0.8.3"

Then do a bundle check to make sure we have the gems we need:

$ bundle check
The Gemfile's dependencies are satisfied

All good (if that gave you an error, just run bundle install).

Now the final step is to wire up the Rails Router.

Open up config/routes.rb and add a require for your twitter app as well as a route to match ‘/twitter’ and send to your Sinatra App, something like this:

require 'twitter/twitter_app'

RackTest::Application.routes.draw do |map|

  match '/twitter', :to => TwitterApp

end

And that’s it!

Fire up your Rails app with rails s as you normally would, and browse to http://127.0.0.1:3000/twitter and proove it to yourself… this stuff works.

Almost too simple.

blogLater

Mikel

  1. Dan Croak Says:
    Sun Feb 07 09:39:54 -0800 2010

    Why lib/twitter.rb? I’ve been placing Sinatra apps in app/metal in Rails 2.

    Also, I’m just learning HTML5 but can’t that xmlns attribute be removed? Looks like you’re mixing the HTML5 DOCTYPE with XHTML stiff.

  2. Rymaï Says:
    Sun Feb 07 10:05:26 -0800 2010

    Awesome! Thanks!

  3. Matt Says:
    Sun Feb 07 11:21:29 -0800 2010

    The xmlns attribute is indeed a remnant of XHTML, but it’s not incorrect to include it: http://diveintohtml5.org/semantics.html

  4. Mikel Lindsaar Says:
    Sun Feb 07 19:46:16 -0800 2010

    Thanks Matt, handled it.

  5. Mikel Lindsaar Says:
    Sun Feb 07 19:47:20 -0800 2010

    @dan because sinatra is not Rails metal and this shows an example of using a separate application within your rails app, as it is not part of your app, it makes sense for it to be in lib.

    The idea being, you could put this app in any rails app and with two lines of code include it.

    Mikel

  6. Marcelo Silveira Says:
    Tue Feb 09 19:01:36 -0800 2010

    Definitely too simple. Thanks.

  7. jc Says:
    Sat Feb 20 06:32:00 -0800 2010

    Shouldnt the sinatra app be get “/” instead of get “/twitter”?

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    @Brian, nice…. I think I will leave it there for prosperity / stupidity value :)

  12. Adam Says:
    Thu Jul 01 19:09:17 -0700 2010

    Thanks for the informative post. I’ve gotten almost everything working nicely but I can’t figure out how to serve static content. I have stylesheet.css in the public folder and I’m not sure how to access it when running the Sinatra app inside a Rails 3 app. Any ideas?

  13. Luis Says:
    Sun Jan 16 02:14:09 -0800 2011

    @Adam

    Couldn’t you do something like:
    dir = File.dirname(File.expand_path(FILE))
    set :public, “#{dir}/public”

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  23. custom OLED displays Says:
    Mon Nov 28 11:50:18 -0800 2011

    class TwitterApp < Sinatra::Base
    "set :root, File.dirname(FILE)

    get ‘/twitter’ do @user = ‘raasdnil’ t = Twitter::Search.new(@user).fetch @tweets = t.results erb :twitter end

    end"

    I am having problems witha tha piece of code, the basic Sinatra app, are you guys facing problems or can you run it well?

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