Undefined Controller In Caction Class

hi,

i follow the wiki How to use a Widget as an Action Provider

in my view i have ajax calls that call to the action.

I want to return the response as an output of renderPartial() function, but my controller is undefined.

$output = $this->getController()->renderPartial('_filterwithManufacturer', array(), true, true);

is there anyway to initiate the controller?
should i passed it as a parameter?

Thanks