Multiple user models with Ruby On Rails and devise to have separate registration routes but one common login route

Okay, so I worked it through and came to the following solution.
I needed to costumize devise a little bit, but it’s not that complicated.

The User model

# user.rb
class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  attr_accessible :email, :password, :password_confirmation, :remember_me

  belongs_to :rolable, :polymorphic => true
end

The Customer model

# customer.rb
class Customer < ActiveRecord::Base
  has_one :user, :as => :rolable
end

The Designer model

# designer.rb
class Designer < ActiveRecord::Base
  has_one :user, :as => :rolable
end

So the User model has a simple polymorphic association, defining if it’s a Customer or a Designer.
The next thing I had to do was to generate the devise views with rails g devise:views to be part of my application. Since I only needed the registration to be customized I kept the app/views/devise/registrations folder only and removed the rest.

Then I customized the registrations view for new registrations, which can be found in app/views/devise/registrations/new.html.erb after you generated them.

<h2>Sign up</h2>

<%
  # customized code begin

  params[:user][:user_type] ||="customer"

  if ["customer", "designer"].include? params[:user][:user_type].downcase
    child_class_name = params[:user][:user_type].downcase.camelize
    user_type = params[:user][:user_type].downcase
  else
    child_class_name = "Customer"
    user_type = "customer"
  end

  resource.rolable = child_class_name.constantize.new if resource.rolable.nil?

  # customized code end
%>

<%= form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f| %>
  <%= my_devise_error_messages!    # customized code %>

  <div><%= f.label :email %><br />
  <%= f.email_field :email %></div>

  <div><%= f.label :password %><br />
  <%= f.password_field :password %></div>

  <div><%= f.label :password_confirmation %><br />
  <%= f.password_field :password_confirmation %></div>

  <% # customized code begin %>
  <%= fields_for resource.rolable do |rf| %>
    <% render :partial => "#{child_class_name.underscore}_fields", :locals => { :f => rf } %>
  <% end %>

  <%= hidden_field :user, :user_type, :value => user_type %>
  <% # customized code end %>

  <div><%= f.submit "Sign up" %></div>
<% end %>

<%= render :partial => "devise/shared/links" %>

For each User type I created a separate partial with the custom fields for that specific User type, i.e. Designer –> _designer_fields.html

<div><%= f.label :label_name %><br />
<%= f.text_field :label_name %></div>

Then I setup the routes for devise to use the custom controller on registrations

devise_for :users, :controllers => { :registrations => 'UserRegistrations' }

Then I generated a controller to handle the customized registration process, copied the original source code from the create method in the Devise::RegistrationsController and modified it to work my way (don’t forget to move your view files to the appropriate folder, in my case app/views/user_registrations

class UserRegistrationsController < Devise::RegistrationsController
  def create
    build_resource

    # customized code begin

    # crate a new child instance depending on the given user type
    child_class = params[:user][:user_type].camelize.constantize
    resource.rolable = child_class.new(params[child_class.to_s.underscore.to_sym])

    # first check if child instance is valid
    # cause if so and the parent instance is valid as well
    # it's all being saved at once
    valid = resource.valid?
    valid = resource.rolable.valid? && valid

    # customized code end

    if valid && resource.save    # customized code
      if resource.active_for_authentication?
        set_flash_message :notice, :signed_up if is_navigational_format?
        sign_in(resource_name, resource)
        respond_with resource, :location => redirect_location(resource_name, resource)
      else
        set_flash_message :notice, :inactive_signed_up, :reason => inactive_reason(resource) if is_navigational_format?
        expire_session_data_after_sign_in!
        respond_with resource, :location => after_inactive_sign_up_path_for(resource)
      end
    else
      clean_up_passwords(resource)
      respond_with_navigational(resource) { render_with_scope :new }
    end
  end
end

What this all basically does is that the controller determines which user type must be created according to the user_type parameter that’s delivered to the controller’s create method by the hidden field in the view which uses the parameter by a simple GET-param in the URL.

For example:
If you go to /users/sign_up?user[user_type]=designer you can create a Designer.
If you go to /users/sign_up?user[user_type]=customer you can create a Customer.

The my_devise_error_messages! method is a helper method which also handles validation errors in the associative model, based on the original devise_error_messages! method

module ApplicationHelper
  def my_devise_error_messages!
    return "" if resource.errors.empty? && resource.rolable.errors.empty?

    messages = rolable_messages = ""

    if !resource.errors.empty?
      messages = resource.errors.full_messages.map { |msg| content_tag(:li, msg) }.join
    end

    if !resource.rolable.errors.empty?
      rolable_messages = resource.rolable.errors.full_messages.map { |msg| content_tag(:li, msg) }.join
    end

    messages = messages + rolable_messages   
    sentence = I18n.t("errors.messages.not_saved",
                      :count => resource.errors.count + resource.rolable.errors.count,
                      :resource => resource.class.model_name.human.downcase)

    html = <<-HTML
    <div id="error_explanation">
    <h2>#{sentence}</h2>
    <ul>#{messages}</ul>
    </div>
    HTML

    html.html_safe
  end
end

UPDATE:

To be able to support routes like /designer/sign_up and /customer/sign_up you can do the following in your routes file:

# routes.rb
match 'designer/sign_up' => 'user_registrations#new', :user => { :user_type => 'designer' }
match 'customer/sign_up' => 'user_registrations#new', :user => { :user_type => 'customer' }

Any parameter that’s not used in the routes syntax internally gets passed to the params hash. So :user gets passed to the params hash.

So… that’s it. With a little tweeking here and there I got it working in a quite general way, that’s easily extensible with many other User models sharing a common User table.

Hope someone finds it useful.