CI框架配置smarty

<?php// load Smarty library
require_once(APPPATH.'libraries/smarty/Smarty.class.php');

class CI_smarty extends Smarty {
    function __construct() {
        parent :: __construct();
        $this -> template_dir = APPPATH . 'views/';
        $this -> compile_dir = APPPATH . 'cache/compile/';
        $this -> config_dir = APPPATH . 'config';
        $this -> cache_dir = APPPATH . 'cache/';
        $this -> left_delimiter = '<%';
        $this -> right_delimiter = '%>'; 
        $this->caching = true;
        $this->testInstall();
        @$this -> clear_all_cache(); 
        //  $this->config_load('site.conf');
        parse_str($_SERVER['QUERY_STRING'],$_GET);
        $_GET = array_map('urldecode', $_GET);
        if (isset($_GET["_d"]) && $_GET["_d"] == 1) {
            $this -> debugging = true;
        }
    }
    function set($key, $val) {
        $arr = array();
        $arr['v'][$key] = $val;
        //print_r($arr);
        $this -> assign($arr);
    }
}
?>