symfony2:控制器中的服务访问抛出异常"错误:在非对象"上调用成员函数get()

我在src'trollmaster'TrollBundle'Services'DefaultService.php做了一个服务

namespace trollmaster'TrollBundle'DefaultService;
class DefaultService
{
    protected $example;
    protected function exampleFunction()
    {
        return null;
    }
}

我资源' config ' services.yml

:

services:
    trollmaster.default_service:
        class: trollmaster'TrollBundle'DefaultService

和命令php app/console container:debug正确返回了我的服务名称，但是当我想在控制器的构造中调用该服务时:

$this->DefaultService = $this->get("trollmaster.default_service");

看到这个错误:

Error: Call to a member function get() on a non-object

我做错了什么?

---

编辑:

当我想将controller定义为service

/**
 * @Route(service="DefaultController")
 */
class DefaultController

I got error:

ClassNotFoundException: Attempted to load class "DefaultController" from namespace "trollmaster'TrollBundle

$service = $this->get('service');
// ... or ...
$service = $this->container->('service');