为什么我不能从扩展AppController的类中访问CakeRequest对象？

Why does cakePHP complain that $request is undefined? I was following the tutorial that they have up on their site how to make a blog (the hello work of frameworks) and I had been fixing the various errors that i came across in the tutorial code (I figured the tutorial was a little bit out of date) but here is one I haven't been able to fathom. Looking at the api documentation it says that Controller has a $request property. my PostsController extends AppController which extends Controller, so it would make sense that it would have the $requests property, but it doesn't, not even according to print_r.

Here is my code (straight from the tutorial):

class PostsController extends AppController {
    public $helpers = array('Html', 'Form', 'Session');
    public $components = array('Session');
    ...

    public function add() {
        if ($this->request->is('post')) {
            ...
        }
    }
}

here is the error page:

Notice (8): Undefined property: PostsController::$request [APP/controllers/posts_controller.php, line 16]
Code

public function add() {
if ($this->request->is('post')) {

PostsController::add() - APP/controllers/posts_controller.php, line 16
Object::dispatchMethod() - CORE/cake/libs/object.php, line 116
Dispatcher::_invoke() - CORE/cake/dispatcher.php, line 227
Dispatcher::dispatch() - CORE/cake/dispatcher.php, line 194
[main] - APP/webroot/index.php, line 88
Fatal error: Call to a member function is() on a non-object in shared/THS/test/www/MyCake/app/controllers/posts_controller.php on line 16

Thanks for any help you can provide.

According to the files paths that one can see in the error you get, you have not installed Cake 2.x but probably Cake 1.3.

And if the tutorial you are following mentions the CakeRequest class, then you are following the Cake 2.x tutorial...