How to access and manipulate data in Apigility before it is sent to the client?

Question

I'm developing an Apigility driven application based on the Zend Framework 2.

Currently I'm sending the data retrieved in the database directly to the client: a request comes in, the MyResource#fetch(...) or MyResource#fetchAll(...) gets triggered and calls an appropriate method on MyService class, that calls MyMapper to retireve the data with its methods like findFooByBar(...).

Now I'd like to process the data, before the response is sent. How can I do that?

---

The Apigility ZF HAL documentation shows, how to access the entity data between it has been retrieved and sent to the client. Well I tried this out. It's ugly and to much code for such task. And... it doesn't work. I want however post here my attept:

namespace Portfolio;

...

class Module implements ApigilityProviderInterface {

    private $serviceManager;

    public function onBootstrap(MvcEvent $event) {
        $application = $event->getTarget();
        $this->serviceManager = $serviceManager = $application->getServiceManager();
        $viewHelperManager = $serviceManager->get('ViewHelperManager');
        $hal = $viewHelperManager->get('Hal');
        $hal->getEventManager()->attach('renderEntity', array($this, 'onRenderEntity'));
        $hal->getEventManager()->attach('renderCollection', array($this, 'onRenderCollection'));
    }

    public function onRenderEntity($event) {
        $entity = $event->getParam('entity');
        if ($entity->entity instanceof ProjectEntity) {
            $projectEntity = $entity->entity;
            $imageCollection = $this->tempCreateimagesForProject(
                $event, $entity->entity->getId()
            );
            $projectEntity->setImages($imageCollection);
            $event->setParam('entity', $projectEntity);
        }
    }

    public function onRenderCollection($event) {
        $collection = $event->getParam('collection');
        $projectCollection = $collection->getCollection();
        if ($projectCollection instanceof ProjectCollection) {
            foreach ($projectCollection as $key => $projectItem) {
                $tempProject = $projectCollection->getItem($key);
                $tempProject->append(
                    ['images' => $this->tempCreateimagesForProject($tempProject->offsetGet('id'))]
                );
                $projectCollection->getItem($key)->offsetSet($key, $tempProject);
            }
        }
    }

    private function tempCreateimagesForProject(Event $event, $projectId) {
        $imageService = $this->serviceManager->get('Portfolio\V2\Rest\ImageService');
        $imageCollection = $imageService->getImagesForProject($projectId);
        return $imageCollection;
    }

    ...

}

Answer 1

I think using the renderEntity and renderCollection events is not the correct spot to add this kind of resource specific logic. It is more suitable for more general changes or incidental customization.

You can add this logic to your resource listeners. So in your fetch and fetchAll methods in your MyResource class you can add the custom code you currently added in these onRenderEntity and onRenderCollection methods.

So something like this:

class MyResource extends AbstractResourceListener
{
    /**
     * Your image service dependency
     */
    protected $imageService;

    /* ... */

    public function fetch($id)
    {
        $project = $this->projectMapper->fetch($id);

        $imageCollection = $this->imageService->getImagesForProject($project);

        $project->setImages($imageCollection);
        return $project;
    }

    /* ... */

    public function fetchAll($params = array())
    {
        $projects = $this->projectMapper->fetchAll();

        foreach ($projects as $key => $project) {
            $imageCollection = $this->imageService->getImagesForProject($project);
            $project->setImages($imageCollection);
        }

        return $projects;
    }

    /* ... */
}

Answer 2

One possible solution is handling the data in the Hydrator. So we write a custom Hydrator class and enrich the items with nested objects and lists in it. It can look like this:

Portfolio\V2\Rest\Project\ProjectHydrator

...

class ProjectHydrator extends ClassMethods {

    /**
     * @var ImageService
     */
    protected $imageService;

    ...

    /*
     * Doesn't need to be implemented:
     * the ClassMethods#hydrate(...) handle the $data already as wished.
     */
    /*
    public function hydrate(array $data, $object) {
        $object = parent::hydrate($data, $object);
        if ($object->getId() !== null) {
            $images = $this->imageService->getImagesForProject($object->getId());
            $object->setImages($images);
        }
        return $object;
    }
    */

    /**
     * @see \Zend\Stdlib\Hydrator\ClassMethods::extract()
     */
    public function extract($object) {
        $array = parent::extract($object);
        if ($array['id'] !== null) {
            $images = $this->imageService->getImagesForProject($array['id']);
            $array['images'] = $images;
        }
        return $array;
    }

}

It's not a nice solution, since then a part of the model / data retrieving logic gets moved to the hydrator. But it works. Here is shown an implementation of this approach and here is a discussion to this topic on GitHub.

Answer 3

If you are using the ClassMethods Hydrator and your Collection extends \Zend\Paginator\Paginator a good solution without losing the Collection's consistency and not changing anybody's code is to overwrite your getCurrentItems() method.

public class MyResourceCollection // most likely extends Paginator
{
    public function getCurrentItems()
    {
        // getting the original items
        $items = parent::getCurrentItems();
        // as we work with objects $item will be an object
        // when working with objects we use references to them not clones of objects
        // so changes to $item are also present in the collection
        foreach ($collection as $item) {
            $oldSomething = $item->getSomething();
            $item->setSomething('['.$oldSomething.']');
        }
        // $items are now changed, return them
        return $items;
    }
}

I have named the key something not to get confused with the getValue method from other places.

This makes the something value look like [something].