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.