How to render a controller in a custom Twig extension using Symfony2 - symfony

Question

I've written a custom Twig function that should render some HTML. My first idea was to create a new Controller for the rendering logic and use that in the Twig extension. But it does not work as it throws this error when calling {{ button() }} in a template:
FATALERROREXCEPTION: ERROR: CALL TO A MEMBER FUNCTION GET() ON A NON-OBJECT IN /FOO/VENDOR/SYMFONY/SYMFONY/SRC/SYMFONY/BUNDLE/FRAMEWORKBUNDLE/CONTROLLER/CONTROLLER.PHP LINE 106
The Twig extensions basically work (I've already implemented some simple helpers not shown here).
The Controller (unnecessary code stripped):
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
class ButtonController extends Controller {
public function showAction()
{
[...]
return $this->render(
'AcmeDemoBundle:Default:button.html.twig', array($vars)
);
}
}
The Twig extension:
class AcmeExtension extends \Twig_Extension {
public function getFunctions()
{
return array(
new \Twig_SimpleFunction('button', array($this, 'button'), array('is_safe' => array('html'))),
);
}
public function button()
{
$controller = new ButtonController();
return $controller->showAction();
}
}

Answer 1

If I understand, you want, when you call the {{ button() }} function, render a controller.
Why not doing a simple:
{{ render(controller('AcmeDemoBundle:Button:show')) }}
This avoid creating a tricky extension for such an easy task.
If you really, really want to call {{ button() }}, you can create a macro, such as:
{% macro button() %}
{{ render(controller('AcmeDemoBundle:Button:show')) }}
{% endmacro %}
{% from _self.templateName import 'button' %}
And you can now use {{ button() }} on the same template.