Delegate Containers

Introduction

Delegate containers are a way to allow you to register one or multiple backup containers that will be used to attempt the resolution of services when they cannot be resolved via this container.

Usage

A delegate must be a PSR-11 implementation and can be registered using the delegate method.

<?php 

namespace Acme\Container;

use Psr\Container\ContainerInterface;

class DelegateContainer implements ContainerInterface
{
    // ..
}

<?php 

$container = new League\Container\Container();
$delegate  = new Acme\Container\DelegateContainer();

// this method can be invoked multiple times, each delegate
// is checked in the order that it was registered
$container->delegate($delegate);

Now that the delegate has been registered, if a service cannot be resolved via the primary container, it will resort to the has and get methods of the delegates to resolve the requested service.

Retrieving a Delegate

If you need to access a registered delegate later, use the getDelegate method with the delegate’s class name.

<?php

$container = new League\Container\Container();

$container->delegate(
    new League\Container\ReflectionContainer()
);

$reflection = $container->getDelegate(League\Container\ReflectionContainer::class);

This is useful when you need to call delegate-specific methods that are not part of the PSR-11 interface, such as passing runtime arguments to ReflectionContainer::get() (see Auto Wiring).