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Autowiring & Configuration-based Factories

Reflection Factory

Writing a factory class for each and every service that has dependencies can be tedious, particularly in early development as you are still sorting out dependencies.

laminas-servicemanager ships with Laminas\ServiceManager\AbstractFactory\ReflectionBasedAbstractFactory, which provides a reflection-based approach to instantiation, resolving constructor dependencies to the relevant services. The factory may be used as either an abstract factory, or mapped to specific service names as a factory:

use Laminas\ServiceManager\AbstractFactory\ReflectionBasedAbstractFactory;

return [
    /* ... */
    'service_manager' => [
        'abstract_factories' => [
            ReflectionBasedAbstractFactory::class,
        ],
        'factories' => [
            'MyModule\Model\FooModel' => ReflectionBasedAbstractFactory::class,
        ],
    ],
    /* ... */
];

Mapping services to the factory is more explicit and even more performant than in v3.0 due to the ahead of time factory generation.

The factory operates with the following constraints/features:

  • A parameter named $config typehinted as an array will receive the application "config" service (i.e., the merged configuration).
  • Parameters typehinted against array, but not named $config, will be injected with an empty array.
  • Scalar parameters will result in the factory raising an exception, unless a default value is present; if it is, that value will be used.
  • If a service cannot be found for a given typehint, the factory will raise an exception detailing this.

$options passed to the factory are ignored in all cases, as we cannot make assumptions about which argument(s) they might replace.

Once your dependencies have stabilized, we recommend providing a dedicated factory, as reflection introduces a performance overhead.

There are two ways to provide dedicated factories for services consuming ReflectionBasedAbstractFactory:

  1. Usage of the generate-factory-for-class console tool (this will also require to manually modify the configuration)
  2. Usage of the generate-aot-factories console tool which needs an initial project + deployment setup

Alternatives

You may also use the Config Abstract Factory, which gives slightly more flexibility in terms of mapping dependencies:

  • If you wanted to map to a specific implementation, choose the ConfigAbstractFactory.
  • If you need to map to a service that will return a scalar or array (e.g., a subset of the 'config' service), choose the ConfigAbstractFactory.
  • If you need a faster factory for production, choose the ConfigAbstractFactory or create a custom factory.

References

This feature was inspired by a blog post by Alexandre Lemaire.