Once a file has been uploaded there are a multitude of potential tasks, ranging from where to store the files (on disk, Amazon S3, etc) and associating them with models to resizing image files and generating thumbnails. The intricacies of this are beyond the scope of this guide, but there are several plugins designed to assist with these. Two of the better known ones are http://github.com/technoweenie/attachment_fu[Attachment-Fu] and http://www.thoughtbot.com/projects/paperclip[Paperclip].
+NOTE: If the user has not selected a file the corresponding parameter will be an empty string.
Dealing with Ajax