Strategy pattern in Symfony2

Question

I'm trying to build simple service for rendering various types of pages. Basic concept is having something like:

$somePageType = new PageType(...);
$this->get('page.service')->render($somePagetype);

...which would be designed as Strategy pattern. Page types would implement interface with render method and page.service would call it. The problem is I'd like to use Doctrine in page type classes. What are my options here? I'd like to avoid creating service for each of these classes. Is that even possible? Is it possible to make them container aware without being services? Possibly, in the future, some page type might need something more than only Doctrine, so I need to keep in mind also that.

Answer 1

Services are exactly what you want here. Being able to inject the dependencies for the particular strategy in question. Then injecting the particular strategy into the controller (could also be a dynamic renderer that chooses the strategy at runtime).

ContainerAware is a really bad practice, it couples the object in question to all of the services in the container. Thus, I'd strongly recommend avoiding it.

Answer 2

I'm assuming PageType is an example of a strategy class. In that case, you could inject the dependencies by the page.service and you wouldn't need to define the strategies as services.

Each strategy probably depends on different objects and therefore I guess you could make them ContainerAware. Here's an example how to do it

// This is the page.service class
class MyPageService {

    public function render(PageTypeInterface $page_type) {
        $page_type->setContainer($this->container);

        // do stuff
    }
}

// This is the type strategy
class MyStrategyType extends ContainerAware implements PageTypeInterface {
    // you can access the container after MyPageService has injected it.
}

So basically each strategy would extend ContainerAware and the page.service would inject the container.

---

EDIT

If all of your strategies are dependant on the same services, I'd inject them instead of the whole container.

class MyPageService {

    public function render(PageTypeInterface $page_type) {
        $page_type->setService($this->container->get('my_service'));

        // do stuff
    }
}