facebook_authentication.rb

# config/routes.rb
devise_for :users, controllers: { omniauth_callbacks: 'omniauth_callbacks' }
 
# config/initializer/devise.rb
Devise.setup do |config|
  if Rails.env.production?
    fb_key = "fb_key"
    fb_secret = "fb_secret"
  else
    fb_key = "fb_key"
    fb_secret = "fb_secret"
  end
  config.omniauth :facebook, fb_key, fb_secret, { scope: "email, user_birthday" }
end
 
# db/migrate
class DeviseCreateUsers < ActiveRecord::Migration
  def change
    create_table(:users) do |t|
      #...
      t.string   :provider
      t.string   :uid
      t.string   :access_token
    end
  end
end
 
# app/controllers/omniauth_callbacks_controller.rb
class OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def facebook
    @user = User.find_for_facebook_oauth(request.env['omniauth.auth'], current_user)
 
    if @user.valid?
      sign_in @user
    else
      redirect_to sign_in_path(invalid_token: 1)
    end
 
    if user_signed_in?
      flash[:notice] = "Signed in successfully."
      redirect_to '/'
    else
      redirect_to sign_in_path(invalid_token: 1)
    end
  end
end
 
# app/model/user.rb
class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
    :recoverable, :trackable, :omniauthable
 
  def self.find_for_facebook_oauth(auth, signed_in_resources = nil)
    user = User.where(provider: auth.provider, uid: auth.uid).first
 
    unless user
      user = User.new(provider:     auth.provider,
                      uid:          auth.uid,
                      email:        auth.info.email,
                      password:     Devise.friendly_token[0,20],
                      #avatar:       auth.info.image,
                      access_token: auth.credentials.token
                     )
      user.save
    end
 
    user
  end
end