Plugin Managers

It can be useful to compose a plugin manager from which you can retrieve hydrators; in fact, Zend\Hydrator\DelegatingHydrator does exactly that! With such a manager, you can retrieve instances using short names, or instances that have dependencies on other services, without needing to know the details of how that works.

Examples of Hydrator plugin managers in real-world scenarios include:

HydratorPluginManagerInterface

We provide two plugin manager implementations. Essentially, they only need to implement the PSR-11 ContainerInterface, but plugin managers in current versions of zend-servicemanager only implement it indirectly via the container-interop project.

As such, we ship Zend\Hydrator\HydratorPluginManagerInterface, which simply extends the PSR-11 Psr\Container\ContainerInterface. Each of our implementations implement it.

HydratorPluginManager

If you have used zend-hydrator prior to version 3, you are likely already familiar with this class, as it has been the implementation we have shipped from initial versions. The HydratorPluginManager extends the zend-servicemanager AbstractPluginManager, and has the following behaviors:

  • It will only return Zend\Hydrator\HydratorInterface instances.
  • It defines short-name aliases for all shipped hydrators (the class name minus the namespace), in a variety of casing combinations.
  • All but the DelegatingHydrator are defined as invokable services (meaning they can be instantiated without any constructor arguments).
  • The DelegatingHydrator is configured as a factory-based service, mapping to the Zend\Hydrator\DelegatingHydratorFactory.
  • No services are shared; a new instance is created each time you call get().

HydratorPluginManagerFactory

Zend\Hydrator\HydratorPluginManager is mapped to the factory Zend\Hydrator\HydratorPluginManagerFactory when wired to the dependency injection container.

The factory will look for the config service, and use the hydrators configuration key to seed it with additional services. This configuration key should map to an array that follows standard zend-servicemanager configuration.

StandaloneHydratorPluginManager

Zend\Hydrator\StandaloneHydratorPluginManager provides an implementation that has no dependencies on other libraries. It can only load the hydrators shipped with zend-hydrator.

StandardHydratorPluginManagerFactory

Zend\Hydrator\StandardHydratorPluginManager is mapped to the factory Zend\Hydrator\StandardHydratorPluginManagerFactory when wired to the dependency injection container.

HydratorManager alias

Zend\Hydrator\ConfigManager defines an alias service, HydratorManager. That service will point to Zend\Hydrator\HydratorPluginManager if zend-servicemanager is installed, and Zend\Hydrator\StandaloneHydratorPluginManager otherwise.

Custom plugin managers

If you do not want to use zend-servicemanager, but want a plugin manager that is customizable, or at least capable of loading the hydrators you have defined for your application, you should write a custom implementation of Zend\Hydrator\HydratorPluginManagerInterface, and wire it to the HydratorManager service, and/or one of the existing service names.

As an example, if you want a configurable solution that uses factories, and want those factories capable of pulling application-level dependencies, you might do something like the following:

// In src/YourApplication/CustomHydratorPluginManager.php:

namespace YourApplication;

use Psr\Container\NotFoundExceptionInterface;
use Psr\Container\ContainerInterface;
use RuntimeException;
use Zend\Hydrator\HydratorInterface;
use Zend\Hydrator\HydratorPluginManagerInterface;
use Zend\Hydrator\StandaloneHydratorPluginManager;

class CustomHydratorPluginManager implements HydratorPluginManagerInterface
{
    /** @var ContainerInterface */
    private $appContainer;

    /** @var StandaloneHydratorPluginManager */
    private $defaults;

    /** @var array<string, string|callable> */
    private $factories = [];

    public function __construct(ContainerInterface $appContainer)
    {
        $this->appContainer = $appContainer;
        $this->defaults = new StandaloneHydratorPluginManager();
    }

    /**
     * {@inheritDoc}
     */
    public function get($id) : HydratorInterface
    {
        if (! isset($this->factories[$id]) && ! $this->defaults->has($id)) {
            $message = sprintf('Hydrator service %s not found', $id);
            throw new class($message) extends RuntimeException implements NotFoundExceptionInterface {};
        }

        // Default was requested; fallback to standalone container
        if (! isset($this->factories[$id])) {
            return $this->defaults->get($id);
        }

        $factory = $this->factories[$id];
        if (is_string($factory)) {
            $this->factories[$id] = $factory = new $factory();
        }

        return $factory($this->appContainer, $id);
    }

    public function has($id) : bool
    {
        return isset($this->factories[$id]) || $this->defaults->has($id);
    }

    public function setFactoryClass(string $name, string $factory) : void
    {
        $this->factories[$name] = $factory;
    }

    public function setFactory(string $name, callable $factory) : void
    {
        $this->factories[$name] = $factory;
    }
}
// In src/YourApplication/CustomHydratorPluginManagerFactory.php:

namespace YourApplication;

use Psr\Container\ContainerInterface;

class CustomHydratorPluginManagerFactory
{
    public function __invoke(ContainerInterface $container) : CustomHydratorPluginManager
    {
        $config = $container->has('config') ? $container->get('config') : [];
        $config = $config['hydrators']['factories'] ?? [];

        $manager = new CustomHydratorPluginManager($this);

        if ([] !== $config) {
            $this->configureManager($manager, $config);
        }

        return $manager;
    }

    /**
     * @param array<string, string|callable> $config
     */
    private function configureManager(CustomHydratorPluginManager $manager, array $config) : void
    {
        foreach ($config as $name => $factory) {
            is_string($factory)
                ? $manager->setFactoryClass($name, $factory)
                : $manager->setFactory($name, $factory);
        }
    }
}
// in config/autoload/hydrators.global.php or similar:

return [
    'dependencies' => [
        'aliases' => [
            'HydratorManager' => \YourApplication\CustomHydratorPluginManager::class,
        ],
        'factories' => [
            \YourApplication\CustomHydratorPluginManager::class => \YourApplication\CustomHydratorPluginManagerFactory::class
        ],
    ],
    'hydrators' => [
        'factories' => [
            \Blog\PostHydrator::class => \Blog\PostHydratorFactory::class,
            \News\ItemHydrator::class => \News\ItemHydratorFactory::class,
            // etc.
        ],
    ],
];

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