Rails Rant

I recently had the pleasure of creating a Facebook app with Ruby on Rails. At first I thought I might try to write my own code to interact directly with the Facebook API, but after looking at it a bit, I decided I better find some existing software to save me some time. Really the only good choice is Facebooker. rFacebook is also another choice, but it looks like it was abandoned a while ago. Apparently Facebook has made quite a few changes to the API in the last year or so. After diving into development I found that Facebooker is not exactly up to date either. A workaround is pretty easy to code, so I will show you that here.

First thing you want to do when creating a facebook app is to log on to Facebook Developer -> http://www.facebook.com/developers/. They have 2 sites for this and dont ask me why. The other one is developer.facebook.com. Do not use that one, because there is no way to edit your app from that page.

From http://www.facebook.com/developers/, click “Set up New Application” and enter an app name. After that you will go to the “Edit” screen for your application. There are a ton of different things you can configure, like the icon, etc.., but for now you just need to worry about your canvas settings. Click “Canvas” in the left side menu. Enter a name for your app: http://apps.facebook.com/your-app-name-goes-here . Next is the most important part, the “Canvas Callback URL”. For this, you need to enter the URL of your application. Since this is going to be an iFrame application, your app will be retrieved from your servers. So I entered: http://www.myapp.com/facebook/canvas. Next make sure you select “iFrame” under canvas render method. Save your changes and its time to start coding with Rails

Here is a screenshot of my settings:

You will need to install facebooker as a plugin. Follow the instructions on github – http://github.com/mmangino/facebooker

Rails Stuff
1. Create a controller called “facebook_controller.rb”
2. Add an action for your canvas page. This will be like the welcome page for your application
3. Add “ensure_authenticated_to_facebook” to the top of your controller. I will talk about this in more detail later.

4. Set up your view (canvas.html.erb) with whatever you want in it. “Hello world”

class FacebookController < ApplicationController
  ensure_authenticated_to_facebook

  def canvas
  end
end

Since you are the developer and you set up the app in facebook, it will already be installed in your facebook account. You can test it by going to http://apps.facebook.com/name-of-your-app-goes-here
You should see your app render in the iframe. Now lets move on to where the app actually does something. Create a link in your view to go to another action that will count your friends

canvas.html.erb

Now you need to add the action to your facebook_controller.rb:

def count_friends
  @count = 0
  #this session variable is set automatically by the facebooker plugin
  fbsession = session[:facebook_session]
  #iterate thru your friends.  fbsession.user grabs your user account and then .friends pulls in all your friends
  fbsession.user.friends.each do |user|
    @count += 1
  end
end

count_friends.html.erb

Woopty doo! You have a working facebook app using Ruby on Rails and Facebooker.

Now if you try to send this to your friends it will not work, because of some changes in the facebook api that were not changed in Facebooker. The main problem lies in the install_url. When your friend tries to install the facebook app, it will send them to your website (no iFrame, just your site outside facebook..no good), instead of directing them to your canvas page which contains your website in an iFrame. To fix this I just hardcoded :canvas=>”true” in this method:

starting at line #189 in vendor/plugins/facebooker/lib/facebooker/rails/controller.rb. I commented out one line and hard coded in a value for canvas. Not sure if this breaks anything else, but it seems fine so far. I am guessing facebook changed something with the fb_sig_in_cavas parameter.

      def create_new_facebook_session_and_redirect!
        session[:facebook_session] = new_facebook_session
        next_url = after_facebook_login_url || default_after_facebook_login_url
        #top_redirect_to session[:facebook_session].login_url({:next => next_url, :canvas=>params[:fb_sig_in_canvas]}) unless @installation_required
        top_redirect_to session[:facebook_session].login_url({:next => next_url, :canvas=>"true"}) unless @installation_required
        false
      end

Push this change to your server and restart your app and this should make everything show up in the iframe after the facebook user installs your app.

On a side note: if you try to use “ensure_application_is_installed_by_facebook_user” in your controller, instead of “ensure_authenticated_to_facebook”, you will get the opposite effect when you click on a link within your application. It will turn into an infinite iframe loop. Every time you click it will create another page inside the iFrame