SinatraとOmniAuthでFacebookアカウント利用したログイン＆ログアウトのサンプル

app.rb

require 'rubygems'
require 'sinatra'
require 'haml'
require 'omniauth'
require 'omniauth-facebook'
require 'logger'


class MyApp < Sinatra::Base

  SCOPE = 'email,read_stream'
  ENV['APP_ID'] = "APPID"
  ENV['APP_SECRET'] = "APPSECRET"
  log = Logger.new('app.log')

  use OmniAuth::Builder do
    provider :facebook, ENV['APP_ID'],ENV['APP_SECRET'], :scope => SCOPE
  end
  set :sessions, true
  use Rack::Session::Cookie

  get '/' do
    if session[:uid] == nil
      redirect '/auth/facebook'
    else
      haml :main
    end  
  end

  get '/logout' do
    session.clear
    haml :logout
  end

  get '/auth/:provider/callback' do
    info = request.env['omniauth.auth']
    log.info('finish authenticate!')
    session[:uid] = info["uid"]
    session[:user_name] = info["info"]["name"]
    session[:image]= info["info"]["image"]
    redirect '/'
  end

  get '/auth/failure' do
    @message = params
    haml :fail
  end
end

MyApp.run! :host => 'localhost', :port => 4567

Gemfile

source :rubyforge
gem 'sinatra'
gem 'omniauth'
gem 'omniauth-facebook'
gem 'haml'

logout.haml

!!! 5
%head
%body
  %p= 'Logout success.'
  %a{:href => '/'} Return main page

main.haml

!!! 5
%head
%body
  %h1= "Welcome! user is #{session[:user_name]}"
  %img{:src => session[:image]}
  %p
    %a{:href => '/logout'} logout