Ruby Social Gems: Facebook

This is the third installment in my series about Ruby Social Media Gems. Today, I am focusing on Facebook gems.

Koala Gem

Koala is a gem that interfaces with the various Facebook APIs (Graph API, REST API, Realtime updates, Test users, and OAuth validation. ) I know there are many Facebook-related gems, but Koala is the gem I have chosen for this article.

The Demo Application

The application we are going to build with the Koala gem is the same as what we’ve built with previous articles. We will get all the user data from Facebook into our rails app so we can display it in whatever format we like. Starting with the application:

You can download the full source code of the tutorial form github here

Create a new rails app: rails new rsg_facebook_gem Add the koala, devise, bootstrap, less gems in path/to/project/Gemfile

gem 'devise'
gem 'koala'
gem "less-rails"
gem 'twitter-bootstrap-rails'

And then run bundle install We are going to use bootstrap for the UI component.

Initializing

Before we start we need to run few commands to initialize the project.

Create the User Model and Bootstrap styling

The following commands are found on the github page of the devise project and the twitter bootstrap project To install devise rails generate devise:install To create the user model rails generate devise user rake db:migrate To configure views rails generate devise:views To install bootstrap rails g bootstrap:install To set a layout bootstrap rails g bootstrap:layout application fixed Remove the index file from path/to/project/public/index.html

Application Structure

Controllers

We will only need to create one controller, which will handle the connection to Facebook. This controller will pull the data from the API and push it to our models. rails g controller facebook Add the following line to the beginning of the FacebookController

before_filter :authenticate_user!

Create an application on the Facebook developer site and set the ‘Site URL’ to ‘http://localhost:3000’ and the ‘App Domains’ to ‘localhost’. if you have any problem with setting the callback, you may find a solution in this link. To explore the Graph API, there is a web interface to it called the Graph API Explorer. You can change the permissions from the “Get Access Token” button on the right and add any number of permissions to your access token. You will use this access token directly into your rails app to test with your account. I should note here that you might find a problem with ssl. The simplest way to workaround this problem is run the following line in the console. For our application, we’ve added this line in an initializer file in /path/to/project/config/initializers/openssl.rb

OpenSSL::SSL::VERIFY_PEER = OpenSSL::SSL::VERIFY_NONE

There are more details about this problem in this link. Now we can add a few helper methods to handle the authentication and API queries. Koala provides Authentication with only two lines of code. Facebook sets the application with some default permissions which might not cover the purpose of your application. To add more permissions, go to permissions tab in your application dashboard. There is tons more info about permissions on the facebook docs. index * First, we check if we already have a facebook_oauth_setting object which stores the access_token. If so, we don’t have to redirect the user each time to get the access_token. The access_token is stored in the session. * The first time the user logs in, we create an OAuth object with the app keys and callback, then redirect the user to Facebook to get the permission.

def index
  unless current_user.facebook_oauth_setting
		@oauth = Koala::Facebook::OAuth.new("app_id", "app_secret", "http://#{request.host}:#{request.port}/callback")
		session["oauth_obj"] = @oauth
		redirect_to @oauth.url_for_oauth_code
	else
		redirect_to "/facebook_profile"
	end
end

callback * If the facebook_oauth_setting object is nil, we use the ‘code’ parameter that Facebook sent back to get the access_token. * Create a new FacebookOauthSetting object for that user and redirect the user to the facebook_profile action

def callback
  unless current_user.facebook_oauth_setting
		@oauth = session["oauth_obj"]
		FacebookOauthSetting.create({:access_token => @oauth.get_access_token(params[:code]), :user_id => current_user.id})
		redirect_to "/facebook_profile"
	else
		redirect_to "/"
	end
end

facebook_profile * If the facebook_oauth_setting object exists, use the stored access_token to create an API object. * Get the user profile info, picture, feed, and friends. and set them into instance variables to display in views, you can store them in models if you want.

def facebook_profile
  if current_user.facebook_oauth_setting
		@graph = Koala::Facebook::API.new(current_user.facebook_oauth_setting.access_token)
		@profile = @graph.get_object("me")
		@picture = @graph.get_picture("me")
		@feed = @graph.get_connections("me","feed")
		@friends = @graph.get_connections("me", "friends")
	else
		redirect_to "/"
	end
end

Routes

Add the following to path/to/project/config/routes.rb

match "/callback" => "facebook#callback"
match "/facebook_profile" => "facebook#facebook_profile"
root :to => 'facebook#index'

Views

We should make few changes before running the server. Modify the layout view path/to/project/app/views/layouts/application.html.erb as shown here:

<body>

  <div class="navbar navbar-fixed-top">
    <div class="navbar-inner">
      <div class="container">
        <a class="btn btn-navbar" data-target=".nav-collapse" data-toggle="collapse">
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
        </a>
        <a class="brand" href="#">RsgFacebookGem</a>
        <div class="container nav-collapse">

        </div><!--/.nav-collapse -->
      </div>
    </div>
  </div>

  <div class="container" style="margin-top: 72px;">
      <div class="row">
        <div class="span9">
           <%= yield %>
        </div>

      </div><!--/row-->

    <footer>
      <p>&amp;copy; Company 2012</p>
    </footer>

  </div> <!-- /container -->

  <!-- Javascripts
  ================================================== -->
  <!-- Placed at the end of the document so the pages load faster -->
  <%= javascript_include_tag "application" %>

</body>

Models

Koala covers, as I’ve mentioned before, the following Facebook APIs: Graph API, REST API, Realtime updates, Test users, and OAuth validation. For an overview, the Koala wiki on github is worth a read, along with the Facebook API reference. We’ve focused on the Graph API, which is the primary way to get data in and out of Facebook’s social graph. For more information on the Graph API, here’s a detailed guide which also covers the Graph API Explorer.

User

Go to /path/to/project/app/models/user.rb and add a has_one relationship to our OAuth object:

has_one :facebook_oauth_setting

FacebookOauthSetting

This model will store two values for each user: access_token and user_id. These values are used later to access the Facebook account without asking for permission each time. Run the following commands to create the above model:

rails g model facebook_oauth_setting access_token:string user_id:integer
rake db:migrate

Add the association between the user model and the facebookoauthsetting model: path/to/project/app/models/facebook_oauth_setting.rb

belongs_to :user

Facebook Graph API Explorer

I would like to emphasize, one last time, the importance of the Graph API Explorer and how helpful it can be. The Koala wiki on github covers this part of the API very well with many examples and documentation. Here’s a couple of these examples:

# to get a specific user
# http://graph.facebook.com/koppel
@graph.get_object("koppel")
# => {"name"=>"Alex Koppel", "id"=>"2905623", "last_name"=>"Koppel", "link"=>"http://www.facebook.com/koppel", "first_name"=>"Alex"}

# to get a page's feed
# http://graph.facebook.com/contextoptional/feed
@graph.get_connections("contextoptional", "feed")
# => array_of_stream stories

# to get any user profile picture
# http://graph.facebook.com/koppel/picture
@graph.get_picture("koppel")
# => "http://profile.ak.fbcdn.net/v224/784/109/q2905623_7065.jpg"

# http://graph.facebook.com/search?q=koala
@graph.search("koala")
# => {"data"=> [{"from"=>{"name"=>"Amy", ...}, "id"=>....,
#     "message"=>"My apartment is infested with koala bears...."}]}

@graph.put_wall_post("hey, i'm learning koala")
# => {"id"=>"2905623_123183957698327"}

# navigating feeds
@result = @graph.get_connections('me', 'feed')
# get the next page from the feed and so on
@next_page = @result.next_page

Let’s put it all together and build a simple view to display the stored data. Create a new file facebook_profile.html.erb at path/to/project/app/views/twitter/

<div class="row">
  <div class="span4">
    <div class="thumbnail">
      <img src="<%= @picture %>" style="float: left;margin: 5px;">
      <h4><%= @profile["name"] %></h4>
      <h4><%= @profile["location"]["name"] %></h4>
      <p>Work @<%= @profile["work"][0]["employer"]["name"] %> as <%= @profile["work"][0]["position"]["name"] %></p>
    </div>
  </div>
</div>

<div class="row" style="margin-top: 16px;width: 1000px;">
  <div class="span5">
  <h1>Feeds</h1>
  	<table class="table table-striped">
  	  <tr>
  	  	<th>Story</th>
  	  	<th>Story tags</th>
  	  </tr>
  		<% @feed.each do |f| %>
	  	  <tr>
	  	  	<td><%= f["story"] %></td>
	  	  	<td><%= f["story_tags"]["19"][0]["name"] %></td>
	  	  </tr>
  	  <% end %>
  	  <% feed_next_page = @feed.next_page %>
  	  <% feed_next_page.each do |f| %>
	  	  <tr>
	  	  	<td><%= f["story"] %></td>
	  	  	<td><%= f["story_tags"]["19"][0]["name"] if f["story_tags"]["19"] %></td>
	  	  </tr>
  	  <% end %>
  	  <% feed_next_page = @feed.next_page %>
  	  <% feed_next_page.each do |f| %>
	  	  <tr>
	  	  	<td><%= f["story"] %></td>
	  	  	<td><%= f["story_tags"]["19"][0]["name"] if f["story_tags"]["19"] %></td>
	  	  </tr>
  	  <% end %>
	</table>
  </div>
	<div class="span5">
	<h1>Friends</h1>
  	<table class="table table-striped">
  	  <tr>
  	  	<th>Name</th>
  	  </tr>
  		<% @friends.each do |f| %>
	  	  <tr>
	  	  	<td><a href="http://facebook.com/<%= f["id"] %>"><%= f["name"] %></a></td>
	  	  </tr>
  	  <% end %>
	</table>
  </div>
</div>

Wrapping Up

I hope this tutorial was useful and a good introduction to using the Koala gem and Facebook APIs. If you would like to suggest the next gem to cover, do so in the comments. Thanks for reading!

Frequently Asked Questions (FAQs) about Ruby Social Gems for Facebook