omniauth_sinatra_example.rb

require 'sinatra/base'
require 'omniauth'


class OmniauthExample < Sinatra::Base
  configure do
    use OmniAuth::Builder do
        provider :facebook, FACEBOOK_APP_ID, FACEBOOK_APP_SECRET, { :scope => 'email, publish_stream' }
        provider :twitter, TWITTER_CONSUMER_KEY, TWITTER_CONSUMER_SECRET
    end
    enable :sessions
  end

  def clear_session
    session[:user_key] = nil
    session[:fb_token] = nil
    session[:fb_error] = nil
  end

  get '/auth/:name/callback' do
    auth = request.env['omniauth.auth']
    # do something
    redirect_to request.env['omniauth.origin'] || '/'
  end
  get '/auth/failure' do
    clear_session
    redirect_to '/'
  end

  get '/signout' do
    clear_session
    redirect '/'
  end
end