can't upload image

My code when upload image class DataFile < ActiveRecord::Base   def self.save(upload)     name = upload['datafile'].original_filename     directory = "public/free"     # create the file path     path = File.join(directory, name)     # write the file     File.open(path, "wb") { |f| f.write(upload['datafile'].read) }   end end but i upload image have name: image1.jpg is it show : undefined method `original_filename' for "images2.jpg":String

I repaired because a multi-part form. Add :multipart=> true to my form_tag.