Resourcen:

• Episode 241: Simple OmniAuth
• OmniAuth
• OmniAuth Identity

bash

rails g model identity name:string email:string password_digest:string
rake db:migrate
rails g controller identities

Gemfile

gem 'omniauth-identity'

config/initializers/omniauth.rb

Rails.application.config.middleware.use OmniAuth::Builder do
  # ...
  provider :identity, on_failed_registration: lambda { |env|
    IdentitiesController.action(:new).call(env)
  }
end

models/identity.rb

class Identity < OmniAuth::Identity::Models::ActiveRecord
  validates_presence_of :name
  validates_uniqueness_of :email
  validates_format_of :email, :with => /^[-a-z0-9_+\.]+\@([-a-z0-9]+\.)+[a-z0-9]{2,4}$/i
end

sessions/new.html.erb

<p>
  <strong>Don't use these services?</strong>
  <%= link_to "Create an account", new_identity_path %> or login below.
</p>

<%= form_tag "/auth/identity/callback" do %>
  <div class="field">
    <%= label_tag :auth_key, "Email" %><br>
    <%= text_field_tag :auth_key %>
  </div>
  <div class="field">
    <%= label_tag :password %><br>
    <%= password_field_tag :password %>
  </div>
  <div class="actions"><%= submit_tag "Login" %></div>
<% end %>

routes.rb

resources :identities

identities_controller.rb

def new
  @identity = env['omniauth.identity']
end

identities/new.html.erb

<%= form_tag "/auth/identity/register" do %>
  <% if @identity && @identity.errors.any? %>
    <div class="error_messages">
      <h2><%= pluralize(@identity.errors.count, "error") %> prohibited this account from being saved:</h2>
      <ul>
      <% @identity.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>
  <div class="field">
    <%= label_tag :name %><br>
    <%= text_field_tag :name, @identity.try(:name) %>
  </div>
  <div class="field">
    <%= label_tag :email %><br>
    <%= text_field_tag :email, @identity.try(:email) %>
  </div>
  <div class="field">
    <%= label_tag :password %><br>
    <%= password_field_tag :password %>
  </div>
  <div class="field">
    <%= label_tag :password_confirmation %><br>
    <%= password_field_tag :password_confirmation %>
  </div>
  <div class="actions"><%= submit_tag "Register" %></div>
<% end %>