I have an invoice form where I'm giving the user opportunity to apply coupons to the invoice total. These coupons are held in another Model and I am going to do a lookup on the Coupon code (something like "20OFFONFRIDAY") which I will use to find what the restrictions and benefits of the coupon. (and to see if it even exists at all)

The invoice does not have "coupon_code" on it so I hand forged the field onto my form with html:

<% if (@invoice.status == 'new') %>
    <input id="coupon_code" name="coupon_code" type="text"/>
<% end %>

and I am calling a controller method with link_to and would like something like the following jquery enhanced link_to to work:

<%= link_to "Apply Coupon", {
        :controller=>"invoices", 
        :id=>@invoice.id, 
        :coupon_code=>$('.coupon_code').val(),
        :action=>"apply_coupon_code" 
    }, 
    :method=>"post" %>

^formatted for easier reading

Then inside my "apply_coupon_code" method I will go off to a couple other models and perform business logic before returning the updated invoice page.

...but maybe it's a pipe dream.

I guess if push came to shove I could add the "coupon_code" field to my invoice model (even though it's persisted elsewhere.) so it's part of the entity and thus easily available on my form to send back into a controller, but I just hate adding a column to make a coupon validation easier.

I figured I'd ping stackoverflow before taking that path.