has_attachment :storage => :file_system,
                 :max_size => 10.megabytes,
                 :thumbnails => { :thumb => '200x200' }

 def validate
   errors.add_to_base("You must choose a file to upload.") unless self.filename

   unless self.filename == nil
     # Images should be less than 10MB
     [:size].each do |attr_name|
       enum = attachment_options[attr_name]
       unless enum.nil? || enum.include?(send(attr_name))
         errors.add_to_base("Files must be smaller than 10MB in size.")
       end
     end

   end
 end