thinkphp自定义业务逻辑有有关问题

thinkphp自定义业务逻辑有问题?
模型:

PHP code

class DepartmentModel extends Model{        public function getIndexDepart()    {        return 1;     }      

PHP code

 
 class IndexAction extends Action 
 { 
     public function index() 
     { 
 $a = D('Department'); 
 echo " <pre>"; 
 print_r($a->getIndexDepart()); 
 echo " </pre>"; 
         //echo THINK_PATH; 
     } 
  
 } 
 

PHP code

class IndexAction extends Action{    public function index()    {        $a = D('Department');[color=#FF0000]        get_class($a);[/color]        echo "<pre>";        print_r($a->getIndexDepart());        echo "</pre>";        //echo THINK_PATH;    }}