将运费加到总计

Question

I am having trouble figuring out how to add shipping cost to my total cart cost in the view of my shopping cart app to calculate an order total.

So far I have ruby code that adds up all of the orders and calculates a order subtotal. I have also added a simple html input form with the shipping options. What I cant figure is how to add the subtotal up with the shipping option that is selected. I feel like there is a simple way to to this in rails but I cant figure out what that would be.

Thanks in advance for any help

_shopping_cart.html.erb

<% if !@order_item.nil? && @order_item.errors.any? %>
  <div class="alert alert-danger">
    <ul>
    <% @order_item.errors.full_messages.each do |msg| %>
      <li><%= msg %></li>
    <% end %>
    </ul>
  </div>
<% end %>
<% if @order_items.size == 0 %>
  <p class="text-center">
    There are no items in your shopping cart.  Please <%= link_to "go back", root_path %> and add some items to your cart.
  </p>
<% else %>
  <% @order_items.each do |order_item| %>
    <%= render 'carts/cart_row', product: order_item.product, order_item: order_item, show_total: true %>
  <% end %>
   <p class="text-center">Order Subtotal=<%= @order_items.sum(:total_price)%></p>
<% end %>
<P class="text-center">Please select shipping:</P>
<P class="text-center"><LABEL ACCESSKEY=C><INPUT TYPE=radio NAME="payment_method" VALUE="2.5" CHECKED> $2.50 US Standard</LABEL><BR>
<LABEL ACCESSKEY=D><INPUT TYPE=radio NAME="payment_method" VALUE="5.5"> $5.50 US Priority</LABEL><BR>
<LABEL ACCESSKEY=M><INPUT TYPE=radio NAME="payment_method" VALUE="9.5"> $9.50 International</LABEL><BR>
<LABEL ACCESSKEY=N><INPUT TYPE=radio NAME="payment_method" VALUE="14.5">  $14.50 International Priority</LABEL></P>

Answer 1

我想你想做：

shipping_cost + cart.total