/**
  * Activate subscription
  * If there is error,set 'error_message' to the template,
  * If activation succeeds, set 'subscriber' to the template
  * @param string: $hashString
  * @return void
  */
 public function activateSubscription($hashString)
 {
     // 1. fetch the subscription object
     $subscription = ezcomSubscription::fetchByHashString($hashString);
     if (is_null($subscription)) {
         $this->tpl->setVariable('error_message', ezpI18n::tr('ezcomments/comment/activate', 'There is no subscription with the hash string!'));
     } else {
         if ($subscription->attribute('enabled')) {
             ezDebugSetting::writeNotice('extension-ezcomments', 'Subscription activated', __METHOD__);
         }
         $subscriber = ezcomSubscriber::fetch($subscription->attribute('subscriber_id'));
         if ($subscriber->attribute('enabled')) {
             $subscription->enable();
             $this->tpl->setVariable('subscriber', $subscriber);
         } else {
             $this->tpl->setVariable('error_message', ezpI18n::tr('ezcomments/comment/activate', 'The subscriber is disabled!'));
         }
     }
 }