Question

I came across a demo with the following line:

 map.current_cart 'cart', :controller => 'carts', :action => 'show', :id => 'current'

Does setting the id to 'current' call the function current_cart by some magic?

application_controller.rb:

 def current_cart
  session[:cart_id] ||= Cart.create!.id
  @current_cart ||= Cart.find(session[:cart_id])
 end

Answer 1

See carts_controller. Method current_cart calls from action show. So there is not any magic: it is just calling method from action and it do the next steps:

1. Creates cart if it has not already existed
2. Stores this cart’s id in session
3. Caches cart in instance variable @current_cart. It will also available in any view
4. Returns in cart’s instance variable
5. saves this returning to @cart variable in show action for carts_controller