README

This package provides a minimalist dependency injection container implementing Psr-11.

The goal is to implement a container working out of the box with minimal configuration, implementing interface aliasing and a basic autowiring mechanism.

• Getting started
• Basic usage
• Interface aliasing
• Autowiring

Getting started

Require php >= 7.4

Installation composer require quanta/container

Run tests php ./vendor/bin/phpunit

Testing a specific php version using docker:

• docker build . --build-arg PHP_VERSION=7.4 --tag quanta/container/tests:7.4
• docker run --rm quanta/container/tests:7.4

Basic usage

• container entries are defined using any iterable as long as keys can be casted as strings
• any non callable value is returned as is like an associative array
• any callable value is treated as a factory building the associated value (the results are cached so the callable is run only once and the same value is returned on every ->get() call)

<?php

// class definitions
final class SomeClass
{
    public function __construct(public SomeDependency $dependency)
    {
    }
}

final class SomeDependency
{
}

// container configuration
$container = new Quanta\Container([
    'id' => 'value',

    SomeClass::class => fn ($container) => new SomeClass(
        $container->get(SomeDependency::class),
    ),

    SomeDependency::class => fn () => new SomeDependency,

    'throwing' => function () {
        throw new Exception('some exception');
    },
]);

// true
$container instanceof Psr\Container\ContainerInterface;
$container->has('id');
$container->has(SomeClass::class);
$container->has(SomeDependency::class);
$container->has('throwing');
$container->get('id') === 'value';
$container->get(SomeClass::class) == new SomeClass(new SomeDependency);
$container->get(SomeDependency::class) == new SomeDependency;
$container->get(SomeClass::class) === $container->get(SomeClass::class);
$container->get(SomeDependency::class) === $container->get(SomeDependency::class);
$container->get(SomeClass::class)->dependency === $container->get(SomeDependency::class);

// false
$container->has('not.defined');

// throws Quanta\Container\NotFoundException
try {
    $container->get('not.defined');
} catch (Quanta\Container\NotFoundException $e) {
    // 'No 'not.defined' entry defined in the container'
    echo $e->getMessage() . "\n";
}

// throws Quanta\Container\ContainerException with the caught exception as previous
try {
    $container->get('throwing');
} catch (Quanta\Container\ContainerException $e) {
    // 'Cannot get 'throwing' from the container: factory has thrown an uncaught exception'
    echo $e->getMessage() . "\n";

    // 'some exception'
    echo $e->getPrevious()->getMessage() . "\n";
}

Interface aliasing

• interface names associated to strings are treated as aliases

// class definitions
interface SomeInterface
{
}

final class SomeImplementation implements SomeInterface
{
}

// container configuration
$container = new Quanta\Container([
    SomeInterface::class => SomeImplementation::class,

    SomeImplementation::class => fn () => new SomeImplementation,
]);

// true
$container->has(SomeInterface::class);
$container->has(SomeImplementation::class);

$container->get(SomeInterface::class) == new SomeImplementation;
$container->get(SomeImplementation::class) == new SomeImplementation;

$container->get(SomeInterface::class) === $container->get(SomeInterface::class);
$container->get(SomeInterface::class) === $container->get(SomeImplementation::class);
$container->get(SomeImplementation::class) === $container->get(SomeImplementation::class);

Autowiring

The container will try to build instances of non defined classes using simple rules to infer constructor parameter values:

• when the type of a parameter is a defined interface name, its value is retrieved from the container
• when the type of a parameter is a class name, its value is retrieved from the container (and also autowired if not defined)
• when the type of a parameter is not an interface/class name, its default value is used if present
• null is used as a fallback when the parameter allows null
• a Quanta\Container\ContainerException is thrown when:
  • no value can be infered for a parameter (not an interface/class name as type, no default value, not allowing null)
  • trying to infer the value of a parameter with union/intersection type, without default value, not allowing null (php 8.0/8.1)
  • trying to autowire an abstract class or a class with protected/private constructor
• the ->has() method returns true for any existing classes
• the objects built through autowiring are cached

A factory must be defined when more control over the class instantiation is needed.

<?php

// class definitions
interface SomeInterface
{
}

final class SomeImplementation implements SomeInterface
{
}

final class AnotherUndefinedClass
{
}

final class UndefinedClass
{
    public function __construct(
        public SomeInterface $dependency1,
        public AnotherUndefinedClass $dependency2,
        public ?int $dependency3,
        public string $dependency4 = 'test',
    ) {
    }
}

// container configuration
$container = new Quanta\Container([
    SomeInterface::class => SomeImplementation::class,
]);

// true
$container->has(SomeInterface::class);
$container->has(SomeImplementation::class);
$container->has(UndefinedClass::class);
$container->has(AnotherUndefinedClass::class);

$container->get(SomeInterface::class) == new SomeImplementation;
$container->get(SomeImplementation::class) == new SomeImplementation;
$container->get(UndefinedClass::class) == new UndefinedClass(new SomeImplementation, new AnotherUndefinedClass, null);
$container->get(AnotherUndefinedClass::class) == new AnotherUndefinedClass;

$container->get(SomeInterface::class) === $container->get(SomeInterface::class);
$container->get(SomeInterface::class) === $container->get(SomeImplementation::class);
$container->get(SomeImplementation::class) === $container->get(SomeImplementation::class);
$container->get(UndefinedClass::class) === $container->get(UndefinedClass::class);
$container->get(AnotherUndefinedClass::class) === $container->get(AnotherUndefinedClass::class);

$container->get(UndefinedClass::class)->dependency1 === $container->get(SomeInterface::class);
$container->get(UndefinedClass::class)->dependency2 === $container->get(AnotherUndefinedClass::class);
$container->get(UndefinedClass::class)->dependency3 === null;
$container->get(UndefinedClass::class)->dependency4 === 'test';