In your specific case you can think that Devise allows your application to authenticate users using a form (ex: by using an email and password) or an authentication token, Omniauth allows your application to "speak" to the Facebook servers to authenticate a user. In other words Omniauth sits on top of Devise and extends the number of ways your user can authenticate.
To implement Facebook login you need to:
0) configure devise: just follow this: https://github.com/plataformatec/devise/wiki/OmniAuth:-Overview
1) expose a link in your view that when clicked by the user will tell Omniauth to start "speaking" to the Facebook server.
=link_to image_tag("facebook_64.png", :size => "64x64", :alt => "Facebook"), user_omniauth_authorize_path(:facebook, :display=>"dialog"), :title=>"Facebook"
2) At one point the Facebook server will call you app so you have to implement a controller to respond to Facebook
class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
before_filter { @omniauth_hash = env["omniauth.auth"] }
# This method is responsible to create a registration_hash given an
# omniaauth_hash
# schama: https://github.com/intridea/omniauth/wiki/Auth-Hash-Schema
def self.build_registration_hash(omniauth_hash={})
if (omniauth_hash["provider"].downcase.eql?("facebook"))
provider = "facebook"
# catch any excpetions thrown by code just to make sure we can continue even if parts of the omnia_has are missing
begin
first_name = omniauth_hash['user_info']['first_name']
last_name = omniauth_hash['user_info']['last_name']
sex = omniauth_hash.fetch('extra', {}).fetch('user_hash',{})['gender']
birthday = Date.strptime(omniauth_hash.fetch('extra', {}).fetch('user_hash', {})['birthday'],'%m/%d/%Y') if omniauth_hash.fetch('extra', {}).fetch('user_hash', {})['birthday']
if omniauth_hash.fetch('extra', {}).fetch('user_hash', {})['timezone']
utc_offset_in_hours = (omniauth_hash.fetch('extra', {}).fetch('user_hash', {})['timezone']).to_i
time_zone = (ActiveSupport::TimeZone[utc_offset_in_hours]).name
else
time_zone = nil
end
locale = omniauth_hash.fetch('extra', {}).fetch('user_hash', {})['locale']
home_town = omniauth_hash.fetch('extra', {}).fetch('user_hash', {}).fetch('location', {})['name']
if omniauth_hash.fetch('user_info', {})['image']
photo_url = (omniauth_hash.fetch('user_info', {})['image']).gsub("=square","=large") #http://graph.facebook.com/531564247/picture?type=square
else
photo_url = nil
end
rescue => ex
logger.error("Error while parsing facebook auth hash: #{ex.class}: #{ex.message}")
sex = nil
birthday = nil
time_zone = nil
locale = nil
home_town = nil
photo_url = nil
end
elsif omniauth_hash['uid'].downcase.include?("google.com")
provider = "google"
if omniauth_hash['user_info']['first_name'] and omniauth_hash['user_info']['last_name']
first_name = omniauth_hash['user_info']['first_name']
last_name = omniauth_hash['user_info']['last_name']
elsif omniauth_hash['user_info']['name']
first_name = omniauth_hash['user_info']['name'].split(' ')[0]
last_name = omniauth_hash['user_info']['name'].split(' ')[1]
else
first_name = nil
last_name = nil
end
sex = nil
birthday = nil
time_zone = nil
locale = nil
home_town = nil
photo_url = nil
elsif omniauth_hash['uid'].downcase.include?("yahoo.com")
provider = "yahoo"
if omniauth_hash['user_info']['first_name'] and omniauth_hash['user_info']['last_name']
first_name = omniauth_hash['user_info']['first_name']
last_name = omniauth_hash['user_info']['last_name']
elsif omniauth_hash['user_info']['name']
first_name = omniauth_hash['user_info']['name'].split(' ')[0]
last_name = omniauth_hash['user_info']['name'].split(' ')[1]
else
first_name = nil
last_name = nil
end
sex = nil
birthday = nil
time_zone = nil
locale = nil
home_town = nil
photo_url = nil
elsif omniauth_hash['uid'].downcase.include?("aol.com")
if omniauth_hash['user_info']['first_name'] and omniauth_hash['user_info']['last_name']
first_name = omniauth_hash['user_info']['first_name']
last_name = omniauth_hash['user_info']['last_name']
elsif omniauth_hash['user_info']['name']
first_name = omniauth_hash['user_info']['name'].split(' ')[0]
last_name = omniauth_hash['user_info']['name'].split(' ')[1]
else
first_name = nil
last_name = nil
end
provider = "aol"
sex = nil
birthday = nil
time_zone = nil
locale = nil
home_town = nil
photo_url = nil
else
provider = "open_id"
if omniauth_hash['user_info']['first_name'] and omniauth_hash['user_info']['last_name']
first_name = omniauth_hash['user_info']['first_name']
last_name = omniauth_hash['user_info']['last_name']
elsif omniauth_hash['user_info']['name']
first_name = omniauth_hash['user_info']['name'].split(' ')[0]
last_name = omniauth_hash['user_info']['name'].split(' ')[1]
else
first_name = nil
last_name = nil
end
sex = nil
birthday = nil
time_zone = nil
locale = nil
home_town = nil
photo_url = nil
end
h = {
:provider => provider,
:email => omniauth_hash['user_info']['email'],
:profile_attributes => {
:first_name => first_name ,
:last_name => last_name,
:avatar_url => photo_url,
:sex => sex,
:birthday => birthday,
:time_zone => time_zone,
:locale => locale,
:location => home_town
}
}
end
def process_callback
# The registration hash isolates the rest of the code from learning all the different structures
# of the omnia_hash
registration_hash = Users::OmniauthCallbacksController.build_registration_hash(@omniauth_hash)
logger.debug(registration_hash.to_yaml)
# Set the @user to nil
@user = nil
# Find if an authentication token for this provider and user id already exists
authentication = Authentication.find_by_provider_and_uid(@omniauth_hash['provider'], @omniauth_hash['uid'])
if authentication # We found an authentication
if user_signed_in? && (authentication.user.id != current_user.id)
flash[:error] = I18n.t "controllers.omniauth_callbacks.process_callback.error.account_already_taken",
:provider => registration_hash[:provider].capitalize,
:account => registration_hash[:email]
redirect_to edit_user_account_path(current_user)
return
end
else
# We could not find the authentication than create one
authentication = Authentication.new(:provider => @omniauth_hash['provider'], :uid => @omniauth_hash['uid'])
if user_signed_in?
authentication.user = current_user
else
registration_hash[:skip_confirmation] = true
authentication.user = User.find_by_email(registration_hash[:email]) || User.create_user(registration_hash)
end
end
@user = authentication.user
# save the authentication
authentication.token = @omniauth_hash
authentication.provider_name = registration_hash[:provider]
authentication.provider_username = registration_hash[:email]
if !authentication.save
logger.error(authentication.errors)
end
# If a user is signed in then he is trying to link a new account
if user_signed_in?
if authentication.persisted? # This was a linking operation so send back the user to the account edit page
flash[:success] = I18n.t "controllers.omniauth_callbacks.process_callback.success.link_account",
:provider => registration_hash[:provider].capitalize,
:account => registration_hash[:email]
else
flash[:error] = I18n.t "controllers.omniauth_callbacks.process_callback.error.link_account",
:provider => registration_hash[:provider].capitalize,
:account => registration_hash[:email],
:errors =>authentication.errors
end
redirect_to edit_user_account_path(current_user)
else
# This was a sign in operation so sign in the user and redirect it to his home page
if @user.persisted? && authentication.persisted?
flash[:success] = I18n.t "controllers.omniauth_callbacks.process_callback.success.sign_in",
:provider => registration_hash[:provider].capitalize,
:account => registration_hash[:email]
sign_in_and_redirect(:user,@user)
else
session['registration_hash'] = registration_hash
flash[:error] = I18n.t "controllers.omniauth_callbacks.process_callback.error.sign_in",
:provider => registration_hash[:provider].capitalize,
:account => registration_hash[:email]
redirect_to new_registration_users_url
end
end
end
def facebook
process_callback
end
def gmail
process_callback
end
Now you will notice that I call a User.create_user(registration_hash). This method implementation will depend on how your app create a user but at the minimum the method has to create a user and assign to it a random password:
def self.create_user(registration_hash)
logger.info "Creating new user with registration hash: #{registration_hash.to_yaml}"
unless registration_hash or resigration_hash.empty?
return nil
end
user = User.new
user.email = registration_hash[:email]
if registration_hash[:password]
user.password = registration_hash[:password]
else
user.password = Devise.friendly_token[0,20]
end
user.password_confirmation = user.password
# custom app code here...
if registration_hash[:skip_confirmation] == true
user.confirm!
end
user
end
Note: My app support login with other service so I have implemented a table that contain authentication tokens.
Hope this can get you started.
