How To: Make Devise work with other formats like mobile, iPhone and iPad (Rails specific)

1. Make your app render Apple iOS templates for iOS devices like iPhone, iPad, iPod Touch, etc.

   Add the following to app/controllers/application_controller.rb:

   # app/controllers/application_controller.rb
   
   class ApplicationController < ActionController::Base
     before_filter :adjust_format_for_iphone
   
     private
   
     def adjust_format_for_iphone    
       request.format = :ios if request.env["HTTP_USER_AGENT"] =~ %r{Mobile/.+Safari}
     end
   end

2. Set Devise to display views for iOS.

   Add every desired format to config.navigational_formats in config/initializers/devise.rb.

   # config/initializers/devise.rb
   
   ...
   config.navigational_formats = [:"*/*", "*/*", :html, :ios]
   ...

3. Create each view you need for Devise (login form, signup form, etc.).

   Name your view something like new.**ios**.erb, e.g. app/views/devise/sessions/new.ios.erb for login form.

4. Create an initializer in config/initializers (e.g. config/initializers/mobile_formats.rb) with the following:

   # config/initializers/mobile_formats.rb
   
   ActionController::Responder.class_eval do
     alias :to_ios :to_html
   end

5. Add your format to config/initializers/mime_types.rb

   # config/initializers/mime_types.rb
   
   Mime::Type.register_alias "text/html", :ios

6. Note that if you use OAUTH for Facebook you will need to configure it to use facebook's mobile authentication path. This post explains how.