Container Awareness

Container Awareness

The Projek Container provides a mechanism to automatically inject the container instance into your services using the ContainerAware interface and HasContainer trait.

Usage

To make a class "container aware," implement the Projek\Container\ContainerAware interface. You can use the Projek\Container\HasContainer trait to provide a standard implementation.

use Projek\Container\ContainerAware;
use Projek\Container\HasContainer;

class MyService implements ContainerAware
{
    use HasContainer;

    public function doSomething()
    {
        // Access the container instance
        $container = $this->getContainer();
        
        // Or fetch another service from the container
        $otherService = $this->getContainer(OtherService::class);
    }
}

How it works (Zero-Config)

As of version 1.x, Container Awareness is powered by the PSR-14 Event System.

Automatic injection works out-of-the-box using a minimalist internal event dispatcher. When a service is resolved, the container dispatches an AfterResolution event. An internal ListenerProvider listens for this event and calls setContainer($this) on any instance implementing the ContainerAware interface.

Using a Custom Dispatcher

If you provide your own PSR-14 EventDispatcher, you must ensure that the container's internal ListenerProvider is registered if you want to keep automatic ContainerAware injection working:

use Projek\Container\Events\ListenerProvider;

$provider = new ListenerProvider();
$provider->setContainer($container);

// Add $provider to your custom dispatcher's listener stack...

The getContainer() method

The HasContainer trait provides a flexible getContainer() method:

1. Without arguments: Returns the Psr\Container\ContainerInterface instance.
2. With a string argument: Treats the argument as a service ID and returns the corresponding service from the container (equivalent to calling $container->get($id)).

// Returns the container itself
$container = $this->getContainer();

// Returns the 'logger' service from the container
$logger = $this->getContainer('logger');

Why use Container Awareness?

While dependency injection through the constructor (autowiring) is generally preferred, Container Awareness is useful for:

• Optional dependencies: When a service might need access to many other services but only in specific scenarios.
• Service Locators: In architectural patterns where a class needs to dynamically fetch services.
• Legacy integration: When you cannot easily change a class constructor.