Advanced Rails - Building Industrial-Strength Web Apps in Record Time

What Is REST? | 199

# Remove specified item from cart

session[:cart].delete product_id.to_i

end

def empty

session[:cart] = Cart.new

end

protected

def set_cart

session[:cart] ||= Cart.new

end

end

config/routes.rb
map.add_to_cart '/carts/add_product/:id',
:controller => 'carts', :action => 'add_product'
map.update_cart_quantity '/carts/update_quantity/:id',
:controller => 'carts', :action => 'update_quantity'
map.remove_product '/carts/remove_product/:id',
:controller => 'carts', :action => 'remove_product'
map.empty_cart '/carts/empty',
:controller => 'carts', :action => 'empty'

We are using named routes here so that we gain the benefit of the Rails

named URI generators. For non-RESTful Rails applications, named

routes are much preferred over the default:controller/:action/:id

route, as they decouple URIs from their implementation. For example,

the “remove product” action in the views would typically be coded as

follows:

link_to "Remove Product",

remove_product_path(:id => @product.id),

:method => :post

If all links are generated through the Rails named route mechanism,

then URIs can be changed simply by changing the template in the

routes file, without touching any of the code that links to the page

being changed.

Though this is a relatively clean implementation, it still requires the use of persistent
session storage on the server. This is not optimal, for the reasons we discussed
earlier.

In addition, this code could use some architectural cleanup. Because a resource can
be anything, we will choose to model the cart as a resource itself. Rather than URIs
affecting the product, which have effects on the cart in the session, we choose
URIs thatexplicitly model their effects on our newly created cart resource. Using
some standard RESTful Rails URI conventions, we come up with the following set of
actions.