Getting Your Existing Rails App on Facebook
There’s a ton of information already out there about writing a new Facebook app with Ruby on Rails. You use facebooker, you call a method at the top of your application_controller and you’re done. It’s pretty easy. The problem is that when you have an existing Rails app and you want to extend it to support alternate fbml views for a Facebook application, things are a bit trickier.
Here’s how I did it:
You’ll have to start with the usual setup:
- Create a Facebook app from the Developer Application
- Install the plugin
- Setup your ssh tunnel for development
- Setup your config/facebook.yml
After you get that done, it’s time to start serving authenticated fbml views for requests coming from Facebook. In the facebooker world, you need to call ensure_authenticated_to_facebook. Unfortunately, if you do that in your application_controller, it will try and do a Facebook authentication for every request coming into your application, not just the ones actually coming from Facebook. Since you are trying to extend your existing application with Facebook views, this isn’t what you want.
It turns out that facebooker does two very important things for you by just having the plugin configured in your application. The first is that it forces the format of all of the Facebook requests to be fbml. Next, it adds an object to session[:facebook_session]. It’s safe to say that if your request has a format of fbml and there is something in session[:facebook_session], you’ve got yourself a Facebook request.
To catch and authenticate just the requests coming from Facebook, you’ll want to add the next bit of code to your application_controller:
before_filter :require_login_for_facebook
def require_login_for_facebook
if params[:format] == 'fbml'
ensure_authenticated_to_facebook
if !session[:facebook_session].nil?
# we'll do something with users
# here in the next post about fb
end
end
end
Now, let’s say you have a movies_controller that uses an app/views/layouts/movies.html.erb layout. You’ll want to add an app/views/layouts/movies.fbml.erb layout for requests coming from Facebook. Next, you want a Facebook specific view for your index action. You already have an app/views/movies/index.html.erb right? Well, just add an app/views/movies/index.fbml.erb.
That’s it, you’re done! Now, when a request comes into your regular application for /movies, the regular index.html.erb view will be rendered inside of your regular movies.html.erb template. But, when a request comes in from your Facebook application to /fb-app-name/movies, it’s authenticated with facebooker, the facebook user will have to have added your application and your new index.fbml.erb view will automatically be rendered inside of your movies.fbml.erb layout.
I will post another article soon talking about how to approach integrating your existing user base with a Facebook user base.
Like this article? Be sure to read the second article in this series titled: “Making Your Existing User Base Play Nice With Your Facebook User Base”.
