Smarty の読み込みに関する問題

smarty加载出现问题
init.inc.php

PHP code

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define ( '__ROOT__', str_replace ( '\\', '/', dirname ( __FILE__ ) ) );
include 'Ext/Smarty.class.php';
class Tpl extends Smarty {
    function __construct() {
        $this->setTemplateDir ( __ROOT__."/View" );
        $this->setCompileDir (__ROOT__."./comp_c" );
        $this->left_delimiter = "<{";
        $this->right_delimiter = "}>";
        parent::__construct();
    }
}

index.php

PHP code

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include 'init.inc.php';
class Index extends Tpl {
    function index(){
        $this->assign('m','asdfasdfasdf');
        
        $this->display('index.html');
    }
}
$tpl = new Index();
$tpl->index();

用的Smarty-3.1.11版本 报错信息是:

PHP code

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Fatal error: Call to a member function createTemplate() on a non-object in D:\AppServ\www\smarty\Ext\sysplugins\smarty_internal_templatebase.php on line 47

只是我用普通的方法就不会出现问题 比如： 

PHP code

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$smarty = new Smarty();
$smarty->setTemplateDir ( __ROOT__ . "/View" );
$smarty->setCompileDir ( __ROOT__ . "/comp_c" );
$smarty -> left_delimiter="<{";
$smarty -> right_delimiter="}>";

include "init.inc.php";
$smarty->display("demo.tpl");

找了一天都没有解决，不知道哪里出现问题 求帮忙…

------解决方案--------------------
你 print_r($this->Smarty); 看看
应该是没有实例化成功，即 $this->Smarty 不是 Smarty 对象