README

Neat service components provide a clean and expressive API for your application to provide, access and inject services and other dependencies. The PSR-11 container interface is implemented for optimal interoperability.

Getting started

To install this package, simply issue composer on the command line:

composer require neat/service

Service Container

The included service container allows you to register and retrieve service instances using factories and preset instances.

<?php

// First whip up a new container
$container = new Neat\Service\Container();

// Then teach it how to create a service
$container->set(PDO::class, function () {
    return new PDO('sqlite:memory');
});

// And retrieve it using has and get methods
if ($container->has(PDO::class)) {
    $pdo = $container->get(PDO::class);
}

Service aliases

To reference a service you won't always want to use the full class name. Not just for conveniences sake, but also to decouple your code from its dependency implementations.

<?php

/** @var Neat\Service\Container $container */

// Suppose we want to access the Neat\Database\Connection service by an alias
$container->alias(PDO::class, 'db');

// Now we can access a service by its db alias
$container->set('db', function() {
    return new PDO('sqlite:memory');
});

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

You can also use aliases to make a service available by an interface name. This will come in handy when using dependency injection.

Service providers

To help you setup multiple services, you can define a service provider which is nothing more than an object with public service factory methods.

<?php

/** @var Neat\Service\Container $container */

class Services
{
    public function now(): DateTime
    {
        return new DateTime('now');
    }

    // Notice how this depends on the service above, the container will
    // automatically resolve this dependency for us.
    public function clock(DateTime $time): Example\Clock
    {
        return new Example\Clock($time);
    }
}

// Now register the service provider
$container->register(new Services());

// To get my clock you would simply use
$container->get(Example\Clock::class);

// Or access the service through its alias (the name of the method)
$container->get('clock');

Dependency injection

The container can also create objects and call methods for you with a technique called auto-wiring. This means it will detect, resolve and inject dependencies automatically based on method signatures and parameter types.

<?php

/** @var Neat\Service\Container $container */

// Assuming your container can produce a PDO and Clock object instance
class BlogController
{
    private $db;

    public function __construct(PDO $db)
    {
        $this->db = $db;
    }

    public function getPosts(Example\Clock $clock, string $tag = null) {
        // ...
    }
}

// You'd create a controller and automatically inject the PDO object
$blog = $container->create(BlogController::class);

// Call the getPosts method and have it receive the Clock object
$posts = $container->call([$blog, 'getPosts']);

// You can combine these two calls into one invocation
$posts = $container->call('BlogController@getPosts');

// And pass any arguments you wish to specify or override
$sportsPosts = $container->call('BlogController@getPosts', ['tag' => 'sports']);

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