Arquivos do post "Desenvolvendo uma Aplicação Facebook do Zero com RAILS 3 - Parte 1", link: http://blog.serraduralabs.com/desenvolvendo-uma-aplicacao-facebook-do-zero-2

dashboard_controller.rb

class DashboardController < ApplicationController
  FB_APP_ID     = 'Application ID'
  FB_APP_SECRET = 'App Secret'

  def index
    if authenticated?
      @user    = graph_api_client.get_object('me')
      @friends = graph_api_client.get_connections('me', 'friends')

      friend_ids = @friends.collect { |friend| friend['id'] }
      @genders   = rest_api_client.rest_call('users.getInfo', {:uids => friend_ids, :fields => 'sex'})

      @males   = @genders.count{ |friend| friend['sex'] == 'male'}
      @females = @genders.size - @males
    else
      require_authentication
    end
  end

  def auth
    session[:facebook_token] = oauth.get_access_token(params['code'])
    redirect_to root_path
  end

  private

  def authenticated?
    session[:facebook_token]
  end

  def require_authentication
    redirect_to oauth.url_for_oauth_code
  end

  def graph_api_client
    Koala::Facebook::GraphAPI.new(session[:facebook_token])
  end

  def rest_api_client
    Koala::Facebook::RestAPI.new(session[:facebook_token])
  end

  def oauth
    Koala::Facebook::OAuth.new(FB_APP_ID, FB_APP_SECRET, callback_url)
  end

  def callback_url
    'http://localhost:3000/auth'
  end
end

Gemfile

source 'http://rubygems.org'

gem 'rails', '3.0.7'
gem 'koala', '1.0.0.rc'

group :development, :test do
  gem 'sqlite3'
  gem 'mongrel'
end

# A gem Koala é a responsável em abstrair a API do Facebook.

index.html.erb

</h1>

<p>
  Olá <%=@user['first_name']%>, você tem <%= @friends.count %> amigos.

  <ul>
    <li>
      Homens: <%= @males %> (<%= ((@males / @genders.size.to_f) * 100).round(2) %>%)
    </li>
    <li>
      Mulheres: <%= @females %> (<%= ((@females / @genders.size.to_f) * 100).round(2) %>%)
    </li>
  </ul>
</p>

routes.rb

FbAppClassificadorDeAmigor::Application.routes.draw do
  match "/auth" => "dashboard#auth"

  root :to => "dashboard#index"
end