Read custom config from settings.yml into a Rails 3 app

application_with_config.rb

# needs the "hashie" gem in Gemfile
require 'erb'

module Movies
  class Application < Rails::Application

    # read from "settings.yml" and optional "settings.local.yml"
    settings = ERB.new(IO.read(File.expand_path('../settings.yml', __FILE__))).result
    mash = Hashie::Mash.new(YAML::load(settings)[Rails.env.to_s])
    
    optional_file = File.expand_path('../settings.local.yml', __FILE__)
    if File.exists? optional_file
      optional_settings = ERB.new(IO.read(optional_file)).result
      optional_values = YAML::load(optional_settings)[Rails.env.to_s]
      mash.update optional_values if optional_values
    end
    
    mash.each do |key, value|
      config.send("#{key}=", value)
    end

    # now we can use those settings happily
    initializer "MongoMapper connect" do
      MongoMapper.config = { Rails.env => config.mongodb }
      MongoMapper.connect(Rails.env)
    end
    
    config.middleware.use Twitter::Login,
      :consumer_key => config.twitter.consumer_key, :secret => config.twitter.secret
    
    config.facebook_client = Facebook::Client.new(config.facebook.app_id, config.facebook.secret,
      :user_fields => %w[link name email website timezone movies])

  end
end