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I'd like to inject an array of objects that implement a common interface into one of my services. I am using zend servicemanager as the DI container. I have been reading the docs for quite a bit now and it seems to me that AbstractPluginManager is the way to go. I haven't been able to make it work though. Is there an example using an AbstractPluginManager + Zend Expressive 3 that I can take a look at?

My ultimate goal is to dynamically inject all registered classes that implement a common interface into my service.

Example:

interface I{}
class A implements I{}
class B implements I{}
class C{}

MyService

__construct(array Iimplementations){...}

$service = $container->get('myservice')

$service has Iimplementations

Thanks in advance

Frank
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2 Answers2

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The AbstractPluginManager is mostly for validation and filter plugins. You can create classes and while validating, you can pass specific configuration which makes the filter or validator re-usable.

What you are looking for is probably an abstract factory. You register the factory once and it can create a service for you. In your case with a specific set of dependencies.

interface I{}
class A implements I{}
class B implements I{}

class MyAbstractFactory implements AbstractFactoryInterface
{
    public function canCreate(ContainerInterface $container, $requestedName)
    {
        return in_array('I', class_implements($requestedName), true);
    }

    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
    {
        return new $requestedName(
            $container->get(DependencyFoo::class),
            $container->get(DependencyBar::class)
        );
    }
}

// config/autoload/dependencies.global.php
return [
    'dependencies' => [
        'factories' => [
            // ...
        ],

        'abstract_factories' => [
            MyAbstractFactory::class,
        ],
    ],
];

You can also go crazy and use reflection to detect dependencies if they are different for each class, however that adds a lot of overhead. I think it's easier and more maintainable to create separate factories. And then there is zend-expressive-tooling which is a cli tool that can create factories, handlers and middleware.

xtreamwayz
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  • As a side note, zend service manager provides a built-in [reflection based abstract factory](https://docs.zendframework.com/zend-servicemanager/reflection-abstract-factory/) implementation since version 3.2.0 and according to my personal experience, its working really well. I would give a try even its reflection overhead before implementing a similar one. – edigu Apr 14 '18 at 22:25
  • Thanks guys for taking the time to reply my question. I just saw your responses. I already have a solution in place using the AbstractPluginManager which is doing exactly what I need. I will post it as an answer then you guys can tell me what you think – Frank Apr 16 '18 at 15:53
  • @xtreamwayz Zend ServiceManager loops through the abstract factories only after not finding the dependency using any of the other options I believe(invokables, factories, etc). Also it seems that your abstract factory is creating instances of classes that implement the I interface with the same arguments in the constructor and that is not my case. Please correct me if I am wrong. I am definitely not an expert using the zend servicemanager. Thanks again for your time :) – Frank Apr 16 '18 at 16:39
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/*Getting I concrete implementations via the plugin manager will ensure the implementation of the I interface*/   
class IPluginManager extends AbstractPluginManager
{
   protected $instanceOf = I::class;

   public function getIConcreteImplementations()
   {
       $concreteImpl = [];
       foreach(array_keys($this->factories) as $key)
       {
           $concreteImpl[] = $this->get($key);
       }

       return $concreteImpl;
    }
}
/*IPluginManagerFactory*/
class TransactionSourcePluginManagerFactory
{
  const CONFIG_KEY = 'i-implementations-config-key';

public function __invoke(ContainerInterface $container, $name, array $options = null)
{
    $pluginManager = new IPluginManager($container, $options ?: []);

    // If this is in a zend-mvc application, the ServiceListener will inject
    // merged configuration during bootstrap.
    if ($container->has('ServiceListener')) {
        return $pluginManager;
    }

    // If we do not have a config service, nothing more to do
    if (! $container->has('config')) {
        return $pluginManager;
    }

    $config = $container->get('config');

    // If we do not have validators configuration, nothing more to do
    if (! isset($config[self::CONFIG_KEY]) || ! 
      is_array($config[self::CONFIG_KEY])) {
        return $pluginManager;
    }

    // Wire service configuration for validators
    (new Config($config[self::CONFIG_KEY]))->configureServiceManager($pluginManager);

    return $pluginManager;
  }
}
/*In the ConfigProvider of the module or global config*/
class ConfigProvider
{
/**
 * Returns the configuration array
 *
 * To add a bit of a structure, each section is defined in a separate
 * method which returns an array with its configuration.
 *
 */
   public function __invoke() : array
   {
    return [
        'dependencies' => $this->getDependencies(),
        'routes' => $this->getRoutes(),
        'i-implementations-config-key' => $this->getIConcreteImplementations(),
    ];
   }
   public function getIConcreteImplementations() : array
   {
    return [
        'factories' => [
            A::class => AFactory::class,
            B::class => InvokableFactory::class,
        ],
    ];
   }
}
/*I can now be sure that I am injecting an array of I implementations into my Service*/
class ServiceFactory
{
    public function __invoke(ContainerInterface $container) : Service
    {
        $pluginManager = $container->get(IPluginManager::class);

        $impl = $pluginManager->getIConcreteImplementations();

        return new Service($impl);
    }
 }
Frank
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