Probleme fonction find

Bonjour,
je regarde actuellement la video cake php jour 3 et j ai une erreur :

Fatal Error
Error: Call to a member function find() on a non-object 
File: F:\wamp\www\2.7\app\Controller\PostsController.php    
Line: 48

Notice: If you want to customize this error message, create app\View\Errors\fatal_error.ctp

( ! ) Xdebug: user triggered in F:\wamp\www\2.7\lib\Cake\View\Errors\fatal_error.ctp on line 37
Call Stack
#   Time    Memory  Function    Location
1   0.0008  265448  {main}( )   ..\index.php:0
2   0.0297  2832608 Dispatcher->dispatch( ) ..\index.php:118
3   0.0444  3759024 Dispatcher->_invoke( )  ..\Dispatcher.php:167
4   0.0463  3832472 Controller->invokeAction( ) ..\Dispatcher.php:193
5   0.0463  3833024 invokeArgs ( )  ..\Controller.php:490
6   0.0463  3833176 PostsController->category( )    ..\Controller.php:490
7   0.0559  4724152 App::shutdown( )    ..\App.php:0
8   0.0563  4724984 App::_checkFatalError( )    ..\App.php:906
9   0.0563  4726200 call_user_func:{F:\wamp\www\2.7\lib\Cake\Core\App.php:933} ( )  ..\App.php:933
10  0.0563  4726424 ErrorHandler::handleError( )    ..\App.php:933
11  0.0564  4727168 ErrorHandler::handleFatalError( )   ..\ErrorHandler.php:213
12  0.0571  4730032 call_user_func:{F:\wamp\www\2.7\lib\Cake\Error\ErrorHandler.php:274} ( )    ..\ErrorHandler.php:274
13  0.0571  4730272 ErrorHandler::handleException( )    ..\ErrorHandler.php:274
14  0.0614  4897296 ExceptionRenderer->render( )    ..\ErrorHandler.php:127
15  0.0614  4898000 call_user_func_array:{F:\wamp\www\2.7\lib\Cake\Error\ExceptionRenderer.php:187} ( ) ..\ExceptionRenderer.php:187
16  0.0614  4898360 ExceptionRenderer->_cakeError( )    ..\ExceptionRenderer.php:187
17  0.0615  4901032 ExceptionRenderer->_outputMessage( )    ..\ExceptionRenderer.php:210
18  0.0615  4901560 Controller->render( )   ..\ExceptionRenderer.php:289
19  0.0752  6517072 View->render( ) ..\Controller.php:960
20  0.0758  6529288 View->_render( )    ..\View.php:473
21  0.0760  6530800 View->_evaluate( )  ..\View.php:933
22  0.0763  6560920 include( 'F:\wamp\www\2.7\lib\Cake\View\Errors\fatal_error.ctp' )   ..\View.php:971
23  0.0836  7126616 xdebug_print_function_stack ( ) ..\fatal_error.ctp:37

et voice mon PostController :

<?php
class PostsController extends AppController {

    /**
     * RequestAction, permet d'avoir la liste des contenus pour le menu
     **/
    function menu(){
        $pages = $this->Post->find('all',array(
            'conditions' => array('type'=>'post','online'=>1),
            'fields' => array('id','slug','name')
            ));
        return $pages;
    }

    function index(){
        $d['posts'] = $this->Paginate('Post',array('type'=>'post','online'=>1 ));
        $this->set($d);
    }

    /**
     * Permet d'afficher une page
     **/
    function show($id = null,$slug = null){
        if(!$id)
            throw new NotFoundException('Aucunes pages ne correspond � cet ID');
        $page = $this->Post->find('first',array(
            'conditions' => array('id' => $id,'type'=>'post')
            ));
        if(empty($page))
            throw new NotFoundException('Aucunes pages ne correspond � cet ID');

        if($slug != $page['Post']['slug'])
            $this->redirect($page['Post']['link'],301);
        $d['page'] = current($page);
        $this->set($d);
    }

    /**
     * 
     **/
    function admin_index(){
        $d['posts'] = $this->Paginate('Post',array('type'=>'post','online >= 0'));
        $this->set($d);
    }

    function category($category){
        $this->loadModel('Caterory');
        $cat = $this->Category->find('first',array(
            'conditions' => array('slug' => $category)
        ));
        if(empty($cat))
            throw new NotFoundException('Aucunes cat�gorie ne correspond � cet ID');
        $d['posts'] = $this->Paginate('Post',array('type'=>'post','online >= 0','category_id' => $cat['Category']['id']));
        $this->set($d);
        $this->render('index');

    }

    function admin_edit($id = null){
        if($this->request->is('put') || $this->request->is('post')){
            if($this->Post->save($this->request->data)){
                $this->Session->setFlash("L'article a bien �t� modifi�","notif");
                $this->redirect(array('action'=>'index'));
            }

        }elseif($id){
            $this->Post->id = $id;
            $this->request->data = $this->Post->read(); 
        }else{
            $this->request->data = $this->Post->getDraft('post');
        }
        $this->loadModel('Category');
        $d['categories'] = $this->Category->find('list');
        $this->set($d);
    }

    function admin_delete($id){
        $this->Session->setFlash('La page a bien �t� supprim�e','notif');
        $this->Post->delete($id);
        $this->redirect($this->referer());
    }
}

Merci d avance :)