AJAX/Form array problem

<%= observe_field("format[id]",
   :frequency => 0.25,
   :update => "infoprijs",
   :url => { :action => :getprijs },
   :with => "'format_id='+encodeURIComponent(value)+
'&quantity='+encodeURIComponent($('quantity[id]').value)+
'&product='+encodeURIComponent($('product[id]').value)") %>

Now to add the options i thought i had to add the following (which is
clearly wrong since ruby keeps hating me for it)

Perhaps I'm missing the point, but couldn't you use Form.serialize?
e.g.
<%= observe_field("format[id]",
    :frequency => 0.25,
    :update => "infoprijs",
    :url => { :action => :getprijs },
    :with => "Form.serialize('form-name')" %>

<%= observe_field("format[id]",
     :frequency => 0.25,
     :update => "infoprijs",
     :url => { :action => :getprijs },
     :with => "Form.serialize('form-name')" %>

The above stuff missed a bracket at last!

Try this...

<%= observe_field("format[id]",
     :frequency => 0.25,
     :update => "infoprijs",
     :url => { :action => :getprijs },
     :with => "Form.serialize('form-name')" ) %>