jquery ui autocomplete in zend form

I have JSON data returned in my action controller:

$results = $repo->getMatchingCityName($searchTerm);

Response that i'm getting:

[{"CityName":"Montreal"},{"CityName":"New york"}]........

But jquery ui autocomplete doesn't show anything

tried

$this->_helper->json(array_values($results));

and

Zend_Json::encode($results);

But no use. How do I convert into

[{"value":"Montreal","label":"Montreal"},{"value":"New york","label":"New york"}]

I got it working like this

$temp = array();
foreach($results as $row)
{
    $value = $row["CityName"];
    array_push($temp, array(
        "label" => $value,
        "value" => $value
    ));
}

$data = $this->_helper->json($temp);
$this->_helper->autoComplete($data);

Added the view helper in bootstrap

Zend_Controller_Action_HelperBroker::addHelper(
    new ZendX_JQuery_Controller_Action_Helper_AutoComplete()
);