Thursday, December 22, 2011

Fixing FBML Facebook apps that use Facebooker

If you've written an FBML Facebook app using the Facebooker (not Facebooker2) library for Ruby on Rails, I'm sure you've noticed by now that it's not working any more. In early to mid November, Facebook changed the way they send requests to all canvas apps (FBML and iFrame). Previously, Facebook would send a bunch of parameters called fb_sig_... where each parameter represented something, like the ID of the user. Then there was an fb_sig parameter which you could use with your secret key to validate that the request came from Facebook. The Facebooker plugin/gem is coded to use this.

In early/mid November they switched to using a single parameter, signed_request. This contains all of the info encoded as JSON, along with a validation signature. They no longer use a "session" to grant access, access is now granted with an OAuth2 key.

Unfortunately if you're still using the original Facebooker library like me, you've got some work on your hands to get your app back to a working state. I'll describe everything I did to get my app working again here.

Install Facebooker2 as a plugin
Development on the Facebooker plugin stopped long ago, the original maintainer started a new Facebooker2 plugin/gem. Unfortunately Facebooker2 doesn't have support for all of the FBML capabilities. There are some similarities between the two but overall Facebooker2 was designed to be MUCH simpler and easier to use, and it definitely is. To put Facebooker2 in your project:
  1. Download Facebooker2 to your vendor/plugins directory
  2. Install the mogli and ruby-hmac gems (how you do this depends on your Rails version, either install it on to the system, specify it as a required gem in your environment.rb file, etc.)
  3. Download the original Facebooker gem/plugin to your lib folder (or just copy it from your vendor folder if you put the code in your project previously).
  4. Edit your config/facebooker.yml file, and change secret_key to secret for your environments.
  5. Edit config/facebooker.yml, and add an app_id property to each environment for your App ID (which can be viewed from the Facebook app page for your app).
  6. Create a file config/initializers/facebooker2.rb and put a single line of code in it:

Modify your ApplicationController
Now that you've got Facebooker2 installed, you'll have to modify your code to use it instead of Facebooker. Modify your ApplicationController to include this code:

Now that you've got this in place, you'll have to edit the rest of your code.

Client and User
Instead of using facebook_session and facebook_session_secured, you'll want to call the methods current_facebook_user and current_facebook_client. current_facebook_user will return a Mogli::User object. Here is some code showing some of the common things you may want to do:

Facebooker Helpers
To include all of the FBML helpers that the Facebooker library includes, add the following code to your application_helper.rb:

You'll also need to make a few changes to the Facebooker helper file. Edit lib/facebooker.../lib/facebooker/rails/helpers.rb and add the following:

If you have named your view files .fbml.erb, you'll need to rename them to just .erb. The .fbml type isn't registered with Facebooker2.

Publishing Stories
Facebooker had this whole publisher syntax to post stories to the users wall. None of this is necessary any more. If you wish to publish stories to a users wall, as long as the user has granted the offline_access permission to your app, do the following:

OK I think that's all there is to it. I have my Facebook app working with these changes.

The Future of FBML
You probably know that Facebook is completely abandoning FBML on June 1, 2012. Converting your app as I described here gives you some time to convert your app's views over to iframe instead of FBML. However, don't be surprised if stuff stops working before then. For instance, I can't get my app to display with https. I'm doing everything correctly but Facebook appears to not support this. Hopefully this blog post will give you some breathing time before June.


John Parker said...

Great article, I have just started to convert a game app written in RoR using Facebooker...

Did you look at Koala? I am having a hard time making a choice between Facebooker2 and Koala...You look like you've covered everything and it might make my decision easier!

Brent said...

I have not looked at Koala. For my particular app Facebooker2 is great and does everything I need it to. However I have not started converting it to an iframe app. I don't know how the Javascript support is. Let me know if you look in to Koala more and what your thoughts are on it.

DreamerForever said...

Do you need to set it as an iframe app or something ?

Brent said...

After June, yes, iframe apps will be the only way to do a Facebook app. This post explains how to get FBML apps temporarily working again until you have your app converted to an iframe app.