I\'m using the following form tag for @jobs which have job_photos included.
<% form_for @jobs, :html => { :multipart => true }, :remote => true d
The thing is that you cannot post a multipart form via AJAX. This is not a rails' limitation. In order to circumvent this, you need to use an iframe technique (which can be easier with responds_to_parent plugin) or use a technology like Flash or Silverlight.
You can use Remotipart gem for file uploads with remote
=> true
.