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!' ) );
            }
        }
    }