Avoid creating a view for each AJAX function at CakePHP - cakephp

Question

I am trying to avoid creating a view for each AJAX function I am using at my controller. (as i don't manipulate the resulting data in any way and in most cases is just a boolean value)
I am using RequestHandler component at my controller:
var $components = array('RequestHandler');
And I added this in routes.php
Router::parseExtensions('json');
I am trying to make this function to work, but I am getting a null value:
public function test(){
$this->layout = 'ajax';
$result = '1';
$this->set('_serialize', $result);
}
To access to the json version of the function i use this URL finishing in .json to avoid loading any view:
http://localhost/cakephp/demoController/test.json
I have been following the steps from CakePHP documentation:
http://book.cakephp.org/2.0/en/views/json-and-xml-views.html#json-and-xml-views
What am I doing wrong? Why don't I get the expecting result and instead I get a null?
Also, if I try to to serialize some array, like this one:
$result = array('demo' => '1');
$this->set('_serialize', $result);
I'm getting this notice:
Notice (8): Undefined index: 1 [CORE\Cake\View\JsonView.php, line 89]Code Context $data = array();
foreach ($serialize as $key) {
$data[$key] = $this->viewVars[$key];$view = null
$layout = null
$serialize = array(
'demo' => '1'
)
$data = array()
$key = '1'JsonView::render() - CORE\Cake\View\JsonView.php, line 89
Controller::render() - CORE\Cake\Controller\Controller.php, line 957
Dispatcher::_invoke() - CORE\Cake\Routing\Dispatcher.php, line 193
Dispatcher::dispatch() - CORE\Cake\Routing\Dispatcher.php, line 161
require - APP\webroot\index.php, line 92
[main] - ROOT\index.php, line 42{"1":null}

Answer 1

As far as I understand the documentation you have to specify a view variable and then refer to this variable when you use the _serialize key. This means your snippet would look like:
$result = '1';
$this->set('theResult', $result);
$this->set('_serialize', array('theResult'));

Answer 2

I don't have the .json extension in the URL and the Router::parseExtensions('json'); line in my routes.php file, so the #dhofstet's answer did not work for me.
My solution was to add the renderAs() call:
public $components = array('RequestHandler');
public function my_ajax_action() {
// do something
$result = '1';
$this->set('result', $result);
$this->set('_serialize', array('result'));
$this->RequestHandler->renderAs($this, 'json');
}

Answer 3

You could create an element and render it.
function test() {
$this->autoRender = false;
$result = array('demo' => '1');
$this->set(compact('result'));
$this->set('_serialize', array('result'));
$this->render(DS.'Elements'.DS.'element_name');
}
See docs

Answer 4

The simplest way is this. Works well for me.
public function fun() {
$this->autoRender = false;
$this->request->onlyAllow('ajax');
$result = array('data1' => 'hello', 'data2' => 'world');
return json_encode($result);
}