README.google_oauth2.md

Using the Google OAuth feature

roo_on_rails provides a pre-baked Omniauth setup to help protect your app with Google authentication. Read the main README first to set things up; you'll need at least GOOGLE_AUTH_ENABLED=YES, and GOOGLE_AUTH_CLIENT_ID and GOOGLE_AUTH_CLIENT_SECRET configured.

Let's build a tiny app that has just a homepage, prompts you to sign in, and show your email once you have.

We add the landing page route:

# config/routes.rb
Rails.application.routes.draw do
  root to: 'landing#index'
end

And a controller/view:

# app/controllers/landing_controller.rb
class LandingController < ApplicationController
  def index
    if session[:email]
      render inline: %{
        You are logged in as <%= session[:email] %>! <br/>
        <%= link_to 'Logout', auth_logout_path %>
      }
    else
      render inline: %{
        You are not logged in <br/>
        <%= link_to 'Login', auth_google_oauth2_path %>
      }
    end
  end
end

The authentication routes get added by roo_on_rails; we need to implement at least session creation, destruction, and handling of failure:

# app/controllers/sessions_controller.rb

class SessionsController < ApplicationController
  def create
    auth_data = request.env['omniauth.auth']
    session[:email] = auth_data.info.email.downcase
    redirect_to root_path
  end

  def destroy
    session.clear
    redirect_to root_path
  end

  def failure
    @error = env['omniauth.error']
    render inline: %{
      Authentication failed: <br/>
      <%= @error.class.name %> <br/>
      <%= @error.message %>
    }
  end
end

And that's it. If you want to blanket-protect a controller, an idiomatic way would be to:

before_filter { redirect_to auth_google_oauth2_path unless session[:email] }

If you dislike the name SessionsController, you can update GOOGLE_AUTH_CONTROLLER to point to a different controller.

You can also change the /auth path prefix used by this feature; in this case you'll want to update the example above. For instance, if you change /auth to /prefix, auth_google_oauth2_path becomes prefix_google_oauth2_path.