rename image before saving via paperclip - rails 2.3.5 -

i using paperclip allow user upload images in rails application.

i want rename images uploaded appending current time file names before saving them in database.

here model. column 'data_file_name' used store image name in 'images' table.

class image < activerecord::base   set_table_name "images"   set_primary_key "id"     before_create : :rename_image_file      def rename_image_file     extension = file.extname(data_file_name).downcase     self.data_file_name.instance_write(:data_file_name, "#{time.now.to_i.to_s}#{extension}")   end      belongs_to :book,:foreign_key => :book_id      has_attached_file :data, :path => ":rails_root/public/book_images/:book_id/:style/:basename.:extension",     :url => "http://www.test.org/book_test_editors/book_images/:book_id/:style/:basename.:extension",     :styles => {     :thumbnails => ["150x172#",:jpg],     :large => ["100%", :jpg]    }    end 

when try upload image, error message below:

 nomethoderror in bookscontroller#update  undefined method `instance_write' "dsc02017.jpg":string 

any help?

note using rails 2.3.5

you can adjust path change file name e.g.

  has_attached_file :data, :path => ":rails_root/public/book_images/:book_id/:style/:basename.#{time.now.to_i}.:extension",