# File lib/google-qr.rb, line 16
  def to_s
    if self.data
      params = ["chl=#{escape_string(self.data)}"]
      params << "chs=#{self.size}"
      params << "choe=#{self.encoding}" if self.encoding
      params << error_correction_params if error_correction_param?
      base_url + params.join("&")
    else
      raise "Attribute @data is required for GoogleQR code"
    end
  end