Sign In With Facebook

Omniauth!

The Omniauth gem allows your app's Users to sign in via their Facebook.

We can then access the User's name and image (so no need for Paperclip!).

Become a Facebook Developer

The first step is to visit developers.facebook.com

Once you're signed in (just your normal FB sign-in),

click on "Apps", and select "Add a New App".

Choose "Website".

Give your App a Name and a Category (I listed mine as "Education").

You should now have access to your APP ID and APP Secret.

It's Gem Time

In a new project, or an existing one without Devise,

add these the two Omniauth gems to your Gemfile:

gem 'omniauth'
gem 'omniauth-facebook', '1.4.0'

And then, of course, in your Terminal run...

$ bundle install

Creating a User Model

$ rails g model User provider uid name oauth_token oauth_expires_at:datetime

Let's generate a model called "User"...

Notice that I only specified the data type for the last attribute?

If you don't specify a DT, the attribute will default to String.

(Yes: I've deliberately wasting your keystrokes this whole time!)

We created a database: don't forget to...

Complete the Model

class User < ActiveRecord::Base
    def self.from_omniauth(auth)
        where(auth.slice(:provider, :uid)).first_or_initialize.tap do |user|
        # if at the end of these slides you end up with an error message,
        # try replace the above line with this:
        # where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
          user.provider = auth.provider
          user.uid = auth.uid
          user.name = auth.info.name
          user.oauth_token = auth.credentials.token
          user.oauth_expires_at = Time.at(auth.credentials.expires_at)
          user.save!
        end
    end

    # the following code pulls user avatars from FB:

    def largeimage
        "http://graph.facebook.com/#{self.uid}/picture?type=large"
    end
  
    def normalimage
        "http://graph.facebook.com/#{self.uid}/picture?type=normal"
    end
end

Fill in the user.rb model with the following code:

Application Controller

We'll need to add some code to our application_controller.rb:

class ApplicationController < ActionController::Base
  # Prevent CSRF attacks by raising an exception.
  # For APIs, you may want to use :null_session instead.
  protect_from_forgery with: :exception

  # add the code shown below:

  def current_user
    @current_user ||= User.find(session[:user_id]) if session[:user_id]
  end
  helper_method :current_user
end

Sessions Controller

Next, we need to create a new Controller.

This controller will have two actions - create and destroy - but we don't necessarily need views associated with those actions, and we'll be augmenting the routes, so it's up to you if you want to do:

$ rails g controller Sessions create destroy

Or you can create the file (sessions_controller.rb) manually in Sublime.

Sessions Controller

However you went about creating it, let's now fill in sessions_controller.rb:

class SessionsController < ApplicationController
    def create
        user = User.from_omniauth(env["omniauth.auth"])
        session[:user_id] = user.id
        redirect_to root_url
    end

    def destroy
        session[:user_id] = nil
        redirect_to root_url
    end
end

Home Controller

So far, we don't actually have a page to visit to test this project out.

So let's just create a Home controller, with one page: Index.

$ rails g controller Home index

Change Your Routes

We'll need some custom routes for the Omniauth-related actions, and then let's set that page we just created (home/index.html.erb)

routes.rb

Rails.application.routes.draw do

  root 'welcome#index'

  match 'auth/:provider/callback', to: 'sessions#create', via: [:get, :post]
  match 'auth/failure', to: redirect('/'), via: [:get, :post]
  match 'signout', to: 'sessions#destroy', as: 'signout', via: [:get, :post]

end

Omniauth Initializer

Within the 'config' folder, and then within the 'initializers' folder, create a new file:

omniauth.rb

OmniAuth.config.logger = Rails.logger

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :facebook, 'APP-ID-HERE', 'APP-SECRET-HERE'
end

In this file you will insert your APP ID and Secret we created way back in the beginning

(@ developers.facebook.com)

Fresh-Brewed JavaScript

Up in our assets/javascripts folder, create a new file called

facebook.js.coffee

jQuery ->
  $('body').prepend('<div id="fb-root"></div>')

  $.ajax
    url: "#{window.location.protocol}//connect.facebook.net/en_US/all.js"
    dataType: 'script'
    cache: true


window.fbAsyncInit = ->
  FB.init(appId: '641667205923336', cookie: true)

  $('#sign_in').click (e) ->
    e.preventDefault()
    FB.login (response) ->
      window.location = '/auth/facebook/callback' if response.authResponse

  $('#sign_out').click (e) ->
    FB.getLoginStatus (response) ->
      FB.logout() if response.authResponse
    true

Of any of the pages presented in these slides, this is one you're gonna want to just copy-n-paste

Back at Home

<div id="user-widget">
  <% if current_user %>
    Welcome <strong><%= current_user.name %></strong>!
    <%= image_tag(current_user.normalimage) %>
    <%= link_to "Sign out", signout_path, id: "sign_out" %>
  <% else %>
    <%= link_to "Sign in with Facebook", "/auth/facebook", id: "sign_in" %>
  <% end %>
</div>

Now, either on home/index.html.erb, or just the application.html.erb view, add Sign In/Sign Out code:

You'll see that once a User signs in through Facebook, we will display their name and FB profile pic.

One Last Step...

Let's go back to developers.facebook.com,

and on the left sidebar you'll see "Settings".

Click on '+Add Platform', choose 'Website', and add your URL.

We're just in development now,

so the URL will be either

http://0.0.0.0:3000or http://localhost:3000

Now It's Time
 To Test It Out!