uma/dic

A minimalistic PSR-11 container

v3.0.0 2021-03-24 16:42 UTC

This package is auto-updated.

Last update: 2021-04-24 17:10:06 UTC


README

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A PSR-11 container focused on human readability and comprehension.

Installation

$ composer require uma/dic:^1.0

Design Goals

Simplicity

A dependency injection container is a rather simple concept and its implementation should be simple, too.

PSR-11 compliance

It must implement the PSR-11 spec, and be usable wherever a PSR-11 container is to be expected.

Setter

It must have a standard way to add dependencies to the container as well as retrieve them. Using a Dependency Injection Container involves these two operations, not just getting them (I'm looking at you PSR-11).

To that end the Container class has a set method and also accepts an optional array of type string => mixed in its constructor, which is equivalent to calling set($id, $entry) with each of its key-value pairs.

Moreover, definitions have to be overridable:

$container = new \UMA\DIC\Container([
  'host' => 'localhost',
  'port' => 8080
]);

$container->set('foo', 'bar');
$container->set('foo', 'baz');
var_dump($container->get('foo'));
// 'baz'

Lazy loading

It must be possible to register lazy services. These are services that are not instantiated until they are actually retrieved for the first time.

This library implements lazy services with anonymous functions. Whenever the container is asked for a service that is actually an anonymous function, that function is executed (passing the container itself as the first parameter) and the result is stored under the same id where the anonymous function used to be.

In addition, the container has a resolved method that returns whether a given service is an anonymous function or not. This can be useful when you need to assert whether a given service has been actually called (or not) on test code.

$container = new \UMA\DIC\Container();
$container->set('dsn', '...');

// A database connection won't be made until/unless
// the 'db' service is fetched from the container
$container->set('db', function(\UMA\DIC\Container $c): \PDO {
  return new \PDO($c->get('dsn'));
});

var_dump($container->resolved('db'));
// false

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

var_dump($container->resolved('db'));
// true

Providers

When a project involves large numbers of services these can be organized in Provider classes.

These classes implement UMA\DIC\ServiceProvider and receive an instance of the container in their provide method. They are then expected to register sets of related services in it. This concept is borrowed from Pimple.

$container = new \UMA\DIC\Container();
$container->register(new \Project\DIC\Repositories());
$container->register(new \Project\DIC\Controllers());
$container->register(new \Project\DIC\Routes());
$container->register(new \Project\DIC\DevRoutes());