ruby on rails - Difference between resource and resources methods

Question

What is the logical difference between resource and resources methods

Here is some examples:

resource :orders, :only => [:index, :create, :show]

> rake routes
 orders POST       /orders(.:format)            orders#create
        GET        /orders(.:format)            orders#show


resources :orders, :only => [:index, :create, :show]

> rake routes
 orders GET        /orders(.:format)            orders#index
        POST       /orders(.:format)            orders#create
  order GET        /orders/:id(.:format)        orders#show


resource :orders

> rake routes
     orders POST       /orders(.:format)            orders#create
 new_orders GET        /orders/new(.:format)        orders#new
edit_orders GET        /orders/edit(.:format)       orders#edit
            GET        /orders(.:format)            orders#show
            PUT        /orders(.:format)            orders#update
            DELETE     /orders(.:format)            orders#destroy


resources :orders

> rake routes
     orders GET        /orders(.:format)            orders#index
            POST       /orders(.:format)            orders#create
  new_order GET        /orders/new(.:format)        orders#new
 edit_order GET        /orders/:id/edit(.:format)   orders#edit
      order GET        /orders/:id(.:format)        orders#show
            PUT        /orders/:id(.:format)        orders#update
            DELETE     /orders/:id(.:format)        orders#destroy

It looks like method resource does not create route for index, and helpers in some cases are different (new_order and new_orders). Why?

Answer 1

At a high level, the intent of resource is to declare that only one of these resources will ever exist. For example:

resource :profile, :only => [:edit, :update]

As a user, I should only be able to update my own profile. I should never be able to edit other users' profiles, so there's no need for a URL scheme like /users/1/profile/edit. Instead, I use /profile/edit, and the controller knows to use the current user's ID rather than the ID passed in the URL (since there is none).

That's why you don't get an index action with resource: there's only one resource, so there's no sense in "listing" them.