h1. Create default Guest user
  class Guest
    def create
      Guest.new
    end

    def has_role? role
      role == :guest
    end

    def has_roles? *roles
      role == :guest
    end
  end  
h2. Add to ApplicationController
  # http://stackoverflow.com/questions/4275058/using-devise-with-guest-users

  def current_user
    super || Guest.create # role defaults to 'guest' in the model.
  end

  def user_signed_in?
    current_user && !current_user.new_record?
  end

  def user_session
    user_signed_in? ? super : session
  end    
h1. Control who can create new users
  $ mkdir app/controllers/users
  $ touch app/controllers/users/registrations_controller.rb  
  class Users::RegistrationsController < Devise::RegistrationsController
    before_filter :check_permissions, :only => [:new, :create, :cancel]
    skip_before_filter :require_no_authentication

    def check_permissions
      authorize! :create, resource
    end
  end  
The check permissions method is really simple. It calls the CanCan method, authorize!, and checks if the current user can create users. We use resource here because devise uses resource to refer to the model that can be authenticated. Also notice how I removed the require_no_authentication filter, a Devise filter which allows access to actions without authentication.
  # replace devise_for :users with:
  devise_for :users,  :controllers => { :registrations => "users/registrations" }  
At this point if you hit the users/sign_up page when not logged in, you will notice that a CanCan::AccessDenied is thrown. This exception is thrown anytime permission is denied so you should customize it to your liking. I put the handler in my ApplicationController:
  class ApplicationController < ActionController::Base
    ...
    rescue_from CanCan::AccessDenied do |exception|
      flash[:error] = exception.message
      redirect_to root_url
    end
    ...
  end  
  class UsersController < ApplicationController
    before_filter :get_user, :only => [:index,:new,:edit]
    before_filter :accessible_roles, :only => [:new, :edit, :show, :update, :create]
    load_and_authorize_resource :only => [:show,:new,:destroy,:edit,:update]

    # GET /users
    # GET /users.xml                                                
    # GET /users.json                                       HTML and AJAX
    #-----------------------------------------------------------------------
    def index
      @users = User.accessible_by(current_ability, :index).limit(20)
      respond_to do |format|
        format.json { render :json => @users }
        format.xml  { render :xml => @users }
        format.html
      end
    end

    # GET /users/new
    # GET /users/new.xml                                            
    # GET /users/new.json                                    HTML AND AJAX
    #-------------------------------------------------------------------
    def new
      respond_to do |format|
        format.json { render :json => @user }   
        format.xml  { render :xml => @user }
        format.html
      end
    end

    # GET /users/1
    # GET /users/1.xml                                                       
    # GET /users/1.json                                     HTML AND AJAX
    #-------------------------------------------------------------------
    def show
      respond_to do |format|
        format.json { render :json => @user }
        format.xml  { render :xml => @user }
        format.html      
      end

    rescue ActiveRecord::RecordNotFound
      respond_to_not_found(:json, :xml, :html)
    end

    # GET /users/1/edit                                                      
    # GET /users/1/edit.xml                                                      
    # GET /users/1/edit.json                                HTML AND AJAX
    #-------------------------------------------------------------------
    def edit
      respond_to do |format|
        format.json { render :json => @user }   
        format.xml  { render :xml => @user }
        format.html
      end

    rescue ActiveRecord::RecordNotFound
      respond_to_not_found(:json, :xml, :html)
    end

    # DELETE /users/1     
    # DELETE /users/1.xml
    # DELETE /users/1.json                                  HTML AND AJAX
    #-------------------------------------------------------------------
    def destroy
      @user.destroy!

      respond_to do |format|
        format.json { respond_to_destroy(:ajax) }
        format.xml  { head :ok }
        format.html { respond_to_destroy(:html) }      
      end

    rescue ActiveRecord::RecordNotFound
      respond_to_not_found(:json, :xml, :html)
    end

    # POST /users
    # POST /users.xml         
    # POST /users.json                                      HTML AND AJAX
    #-----------------------------------------------------------------
    def create
      @user = User.new(params[:user])

      if @user.save
        respond_to do |format|
          format.json { render :json => @user.to_json, :status => 200 }
          format.xml  { head :ok }
          format.html { redirect_to :action => :index }
        end
      else
        respond_to do |format|
          format.json { render :text => "Could not create user", :status => :unprocessable_entity } # placeholder
          format.xml  { head :ok }
          format.html { render :action => :new, :status => :unprocessable_entity }
        end
      end
    end
    ...

  # PUT /users/1
   # PUT /users/1.xml
   # PUT /users/1.json                                            HTML AND AJAX
   #----------------------------------------------------------------------------
   def update
     if params[:user][:password].blank?
       [:password,:password_confirmation,:current_password].collect{|p| params[:user].delete(p) }
     else
       @user.errors[:base] << "The password you entered is incorrect" unless @user.valid_password?(params[:user][:current_password])
     end

     respond_to do |format|
       if @user.errors[:base].empty? and @user.update_attributes(params[:user])
         flash[:notice] = "Your account has been updated"
         format.json { render :json => @user.to_json, :status => 200 }
         format.xml  { head :ok }
         format.html { render :action => :edit }
       else
         format.json { render :text => "Could not update user", :status => :unprocessable_entity } #placeholder
         format.xml  { render :xml => @user.errors, :status => :unprocessable_entity }
         format.html { render :action => :edit, :status => :unprocessable_entity }
       end
     end

   rescue
     respond_to_not_found(:js, :xml, :html)
   end
    
    # FILTERS 
    
    
    # Get roles accessible by the current user
    #----------------------------------------------------
    def accessible_roles
      @accessible_roles = Role.accessible_by(current_ability,:read)
    end

    # Make the current user object available to views
    #----------------------------------------
    def get_user
      @current_user = current_user
    end    
  end  
h2. Views
  

Register User

<%= form_for(@user) do |f| %> <%= error_messages(@user,"Could not register user") %> <%= render :partial => 'user_fields', :locals => { :f => f } %>

<%= f.label :password %>

<%= f.password_field :password %>

<%= f.label :password_confirmation %>

<%= f.password_field :password_confirmation %>

<%= f.submit "Register" %>

<% end %>
h3. partial – _user_fields.html.erb
  

<%= f.label :first_name %>

<%= f.text_field :first_name %>

<%= f.label :last_name %>

<%= f.text_field :last_name %>

<%= f.label :email %>

<%= f.text_field :email %>

<% if can? :read, Role %>

<%= f.label :role %>

<% end %>
Only allow editing of role attribute if allowed to! h3. Edit existing user
  

<%= @user == @current_user ? "Your Account Settings" : "Edit User" %>

<%= form_for(@user, :html => { :method => :put }) do |f| %> <%= error_messages(@user,"Could not update user") %> <%= render :partial => 'user_fields', :locals => { :f => f } %>

<%= f.label :password %> (leave blank if you don't want to change it)

<%= f.password_field :password %>

<%= f.label :password_confirmation %>

<%= f.password_field :password_confirmation %>

<%= f.label :current_password %> (we need your current password to confirm your changes)

<%= f.password_field :current_password %>

<%= f.submit "Update" %>

<% end %> <%= link_to "Back", :back %>
h3. Show User
  

<%= @user.name %>

<%= link_to_if(can?(:update,@user), "Edit", edit_user_path(@user)) %> | <%= link_to_if(can?(:delete, @user), "Delete", user_path(@user), :confirm => "Are you sure?", :method => :delete) {} %> <% if can?(:see_timestamps,User) %> <% end %>
Email: <%= @user.email %>
Role: <%= @user.roles.first.name %>
Created at: <%= @user.created_at %>
Last Sign In: <%= @user.last_sign_in_at %>
Sign In Count: <%= @user.sign_in_count %>
h3. Custom can see timestamps!
  if user.role? :admin
    can :see_timestamps, User
  elsif user.role? :normal
    can :see_timestamps, User, :id => user.id
  end  
h3. Recaptcha
  class RegistrationsController < Devise::RegistrationsController

    def create
      if verify_recaptcha
        super
      else
        build_resource
        clean_up_passwords(resource)
        flash[:error] = "There was an error with the recaptcha code below. Please re-enter the code and click submit."
        render_with_scope :new
      end
    end
    .
    .
    .
    .
  end  
h3. Recaptcha with Omniauth
  class RegistrationsController < Devise::RegistrationsController

    def create
      if session[:omniauth] == nil #OmniAuth
        if verify_recaptcha
          super
          session[:omniauth] = nil unless @user.new_record? #OmniAuth
        else
          build_resource
          clean_up_passwords(resource)
          flash[:error] = "There was an error with the recaptcha code below. Please re-enter the code and click submit."
          render_with_scope :new
        end
      else
        super
        session[:omniauth] = nil unless @user.new_record? #OmniAuth
      end
    end  
h2. login with username Customizing The Login Requirements Our application currently uses an email address and password to log users in, but if we want to change it so that it asks for a username instead of an email address then we can do so fairly easily. The first thing we need to do is create a username column in the User table, which we can do by generating a migration. $ rails generate migration add_username_to_users username:string That done we’ll run the migration. $ rake db:migrate As we only have one user in the database we can quickly log in to the Rails console and set a value for the username attribute for that user. $ rails c Loading development environment (Rails 3.0.0.beta2) ruby-1.8.7-p249 > User.first.update_attribute(:username, "eifion") => true Now that we’ve modified the database we need to modify devise’s configuration file, uncommenting the config.authentication_keys line and changing its value from :email to :username. /config/initializers/devise.rb 1. config.authentication_keys = [ :username ] config.authentication_keys = [ :username ] With this value set devise will use the username field as the authentication key. We’ll also have to modify the sign in form so that it has a username field instead of the email field. /app/views/devise/sessions/new.html.erb 1. <% title "Sign In" %> 2. 3. <%= form_for(resource_name, resource, :url => session_path(resource_name)) do |f| %> 4.
    5.
  1. <%= f.label :username %> <%= f.text_field :username %>
  2. 6.
  3. <%= f.label :password %> <%= f.password_field :password %>
  4. 7. <% if devise_mapping.rememberable? -%> 8.
  5. <%= f.check_box :remember_me %> <%= f.label :remember_me %>
  6. 9. <% end %> 10.
  7. <%= f.submit "Sign in" %>
  8. 11.
12. <% end %> 13. 14. <%= render :partial => "devise/shared/links" %> <% title "Sign In" %> <%= form_for(resource_name, resource, :url => session_path(resource_name)) do |f| %>
  1. <%= f.label :username %> <%= f.text_field :username %>
  2. <%= f.label :password %> <%= f.password_field :password %>
  3. <% if devise_mapping.rememberable? -%>
  4. <%= f.check_box :remember_me %> <%= f.label :remember_me %>
  5. <% end %>
  6. <%= f.submit "Sign in" %>
<% end %> <%= render :partial => "devise/shared/links" %> The signup form will also need to be modified and we’ll have to add validation to the User model attribute but we won’t show that here. Once we’ve restarted the server so that the configuration changes are picked up we can visit the signin page and login with a username instead of and email address. h2. me.com and gmail style Another way to do this is me.com and gmail style. You allow an email or the username of the email. For public facing accounts, this has more security. Rather than allow some hacker to enter a username and then just guess the password, they would have no clue what the user’s email is. Just to make it easier on the user for logging in, allow a short form of their email to be used e.g “someone@domain.com” or just “someone” for short. before_create :create_login def create_login email = self.email.split(/@/) login_taken = User.where( :login => email[0]).first unless login_taken self.login = email[0] else self.login = self.email end end def self.find_for_database_authentication(conditions) self.where(:login => conditions[:email]).first || self.where(:email => conditions[:email]).first end