Facebooker configs in database

On a a recent project, I wanted to be able to fetch Facebooker configs from the database instead of the static facebooker.yml config file. This allows for greater flexibility, especially when you need to serve multiple Facebook applications from the same codebase.

In my case, I worked on a donation system on Facebook which is kind of like the Causes Facebook app except that each cause gets its own Facebook app. The Facebook apps are created on the fly from the web admin interface by cause administrators and all the apps point to the same server.

The problem is that Facebooker does not allow serving multiple Facebook applications dynamically. I had to monkey patch it in order to make it work. In my config/initializers folder, I created a new file named facebooker.rb with the following code :

require 'facebooker'

module Facebooker
  class << self  
    def fetch_config_for(api_key)
      cause = Cause.find_by_api_key(api_key)
      if cause
        cause.attributes.merge("callback_url" => Settings.facebook.callback_url)
      else
        false
      end
    end
  end
end

The fetch_config_for method is called on each request to bind the request to a facebook application configuration. The original method looks for the config in facebooker.yml. This methods overrides that to use a database lookup instead. In the Cause model, I have fields named canvas_page_name, api_key and secret_key. The callback_url is the same for all the apps but it will change depending on the environment. I use the settingslogic plugin to handle that.

Don’t forget to leave a dummy facebooker.yml file in the config folder since it’s loaded when the Facebooker plugins initializes.