Rails: Dynamic Select On Multistep Form Not Keeping Selected

I am working on a multistep form for an order placement process following Ryan Bates's Multistep Tutorial #217 which uses a session. On the first step I have two select fields: one

Solution 1:

@shippingservices = @cart.available_shipping_services.joins(:lands).where(:lands => {:id => session[:cart_params]})

This was not correctly using the session[:cart_params] to get the land_id in order to set the orders land when moving back through the form. We can instead use @order = Order.new(session[:order_params]) defined one line above to grab @order.land_id and not have to rely on any of the sessions.

I would also add an existence check if there is a possibility of an Order being initialized without a corresponding Land.