Rails Routes Namespaces and form_for

I have namespace in my routes.rb

  namespace :businesses do
    resources :registration
  end

My controller is in a subdirectory businesses/registration_controller.

def new
  @business = Business.new
end

In my view, I want to do this form_for @business do |f| ... but I am getting the following error:

No route matches {:controller=>"businesses", :action=>"create"}

Restarted the server and I'm also getting this:

undefined method businesses_path' for #<#:0x10339bb20>`

Here are my rake routes:

                   home_index GET    /home/index(.:format)                       {:action=>"index", :controller=>"home"}
             new_user_session GET    /users/sign_in(.:format)                    {:action=>"new", :controller=>"devise/sessions"}
                 user_session POST   /users/sign_in(.:format)                    {:action=>"create", :controller=>"devise/sessions"}
         destroy_user_session GET    /users/sign_out(.:format)                   {:action=>"destroy", :controller=>"devise/sessions"}
                user_password POST   /users/password(.:format)                   {:action=>"create", :controller=>"devise/passwords"}
            new_user_password GET    /users/password/new(.:format)               {:action=>"new", :controller=>"devise/passwords"}
           edit_user_password GET    /users/password/edit(.:format)              {:action=>"edit", :controller=>"devise/passwords"}
                user_password PUT    /users/password(.:format)                   {:action=>"update", :controller=>"devise/passwords"}
     cancel_user_registration GET    /users/cancel(.:format)                     {:action=>"cancel", :controller=>"devise/registrations"}
            user_registration POST   /users(.:format)                            {:action=>"create", :controller=>"devise/registrations"}
        new_user_registration GET    /users/sign_up(.:format)                    {:action=>"new", :controller=>"devise/registrations"}
       edit_user_registration GET    /users/edit(.:format)                       {:action=>"edit", :controller=>"devise/registrations"}
            user_registration PUT    /users(.:format)                            {:action=>"update", :controller=>"devise/registrations"}
            user_registration DELETE /users(.:format)                            {:action=>"destroy", :controller=>"devise/registrations"}
                        users GET    /users(.:format)                            {:action=>"index", :controller=>"users"}
                        users POST   /users(.:format)                            {:action=>"create", :controller=>"users"}
                     new_user GET    /users/new(.:format)                        {:action=>"new", :controller=>"users"}
                    edit_user GET    /users/:id/edit(.:format)                   {:action=>"edit", :controller=>"users"}
                         user GET    /users/:id(.:format)                        {:action=>"show", :controller=>"users"}
                         user PUT    /users/:id(.:format)                        {:action=>"update", :controller=>"users"}
                         user DELETE /users/:id(.:format)                        {:action=>"destroy", :controller=>"users"}
   full_tree_admin_categories GET    /admin/categories/full_tree(.:format)       {:action=>"full_tree", :controller=>"admin/categories"}
             admin_categories GET    /admin/categories(.:format)                 {:action=>"index", :controller=>"admin/categories"}
             admin_categories POST   /admin/categories(.:format)                 {:action=>"create", :controller=>"admin/categories"}
           new_admin_category GET    /admin/categories/new(.:format)             {:action=>"new", :controller=>"admin/categories"}
          edit_admin_category GET    /admin/categories/:id/edit(.:format)        {:action=>"edit", :controller=>"admin/categories"}
               admin_category GET    /admin/categories/:id(.:format)             {:action=>"show", :controller=>"admin/categories"}
               admin_category PUT    /admin/categories/:id(.:format)             {:action=>"update", :controller=>"admin/categories"}
               admin_category DELETE /admin/categories/:id(.:format)             {:action=>"destroy", :controller=>"admin/categories"}
businesses_registration_index GET    /businesses/registration(.:format)          {:action=>"index", :controller=>"businesses/registration"}
businesses_registration_index POST   /businesses/registration(.:format)          {:action=>"create", :controller=>"businesses/registration"}
  new_businesses_registration GET    /businesses/registration/new(.:format)      {:action=>"new", :controller=>"businesses/registration"}
 edit_businesses_registration GET    /businesses/registration/:id/edit(.:format) {:action=>"edit", :controller=>"businesses/registration"}
      businesses_registration GET    /businesses/registration/:id(.:format)      {:action=>"show", :controller=>"businesses/registration"}
      businesses_registration PUT    /businesses/registration/:id(.:format)      {:action=>"update", :controller=>"businesses/registration"}
      businesses_registration DELETE /businesses/registration/:id(.:format)      {:action=>"destroy", :controller=>"businesses/registration"}
                         root        /(.:format)                                 {:action=>"index", :controller=>"home"}

If you have namespaced routes the best way is:

class Admin::BusinessesController < ApplicationController
  def new
    @business = Business.new
  end
end

in routes.rb:

namespace :admin do
  resources :businesses
end

In view:

form_for [:admin, @business] do |f|...

The Docs: http://guides.rubyonrails.org/form_helpers.html section 2.3.1 Dealing with Namespaces

Regarding your case:

In routes.rb everything is o'k. In the view you should write url explicitly because you have variable in controller other than controller name:

form_for @business, :url => business_registration_path do |f|...

I suppose that in businesses/registration_controller you have something like this:

class Businesses::RegistrationController < ApplicationController
  def new
    @business = Business.new
  end
end

And one remark: I wouldn't create registration_controller for registering a new business. I think that keeping business related actions in business_controller is much clearer.

Actually, I think there is a better solution.

form_for [:admin, @business]

the issue with giving a url is that if you abstract the form out as a partial view, you'll need to deal with "create" and "update" situations. They points to different urls, and ends up with providing the @url in controller.