How to: Use a timestamp in file names

You can include a timestamp in filenames overriding the filename as you can read in Carrierwave docs:

class PhotoUploader < CarrierWave::Uploader::Base
  def filename
    @name ||= "#{timestamp}-#{super}.jpg" if original_filename.present? and super.present?
  end

  def timestamp
    var = :"@#{mounted_as}_timestamp"
    model.instance_variable_get(var) or model.instance_variable_set(var, Time.now.to_i)
  end
end

Note: This does not seem to be reliable. I'd strongly recommend saving the timestamp to the database and reading it from the model to generate the filename instead of using this method.

Don't forget to memoize the result in an instance variable or you might get different timestamps written to the database and the file store.

(Related: How to: Create random and unique filenames for all versioned files)