/**
  * Returns an singleton instance of this class
  * @return
  */
 public static function getInstance()
 {
     if (self::$instance == null) {
         self::$instance = new NewsletterMapper();
     }
     return self::$instance;
 }
 /**
  * Initializes DB mappers
  *
  * @param object $config
  * @param object $args
  * @return
  */
 function __construct($config, $args)
 {
     $this->mapper = NewsletterMapper::getInstance();
     $this->config = $config;
     $this->args = $args;
 }