README

Introduction

The dependency injection container is a powerful tool for managing class dependencies and performing dependency injection. Class dependencies are "injected" into the class via the constructor and resolved by the container.

Example:

class Controller
{
    protected Repository $repository;
    
    public function __construct(Repository $repository)
    {
        $this->repository = $repository;
    }
}

Calling $container->make(Controller::class) would be equal to new Controller(new Repository). This amazing feature resolves all dependency injections automatically with zero-config. For this example if Repository have its own dependency, it will be resolved the same.

Installing

composer require opxcore/container

Creating

You can create a container several ways:

$container = Container::setContainer(new Container);

or

$container = Container::getContainer();

In all of this cases Container::getContainer() will always return the same container instance.

If you want to create and handle a container (or several containers) by yourself just use $container = new Container and handle this container instance as you want.

Registering a binding with the container

Basic binding to container looks like:

$container->bind($abstract, $concrete, $parameters);

$abstract is a string containing class name or shorthand for a name to be resolved.

$concrete is a string containing class name or callable returning object for a name to be resolved to. Container instance and parameters will be passed to callable during resolving.

$parameters is an array or callable returning array with parameters used for resolving (see below). Default value is null means no parameters will be bound.

Examples:

Simple usage

$container->bind('logger', Logger::class);

// New instance of Logger with resolved dependencies will be retuened.
$logger = $container->make('logger');

Binding interfaces to its realizations

We have Controller class what depends on some RepositoryInterface and FileRepository implementing it:

class Controller
{
    protected RepositoryInterface $repository;
    
    public function __construct(RepositoryInterface $repository)
    {
        $this->repository = $repository;
    }
}

class FileRepository implements RepositoryInterface
{
    protected string $path;
    
    public function __construct(string $path)
    {
        $this->path = $path;
    }
}

Now we bind FileRepository::class to RepositoryInterface::class so when some class depends on RepositoryInterface it will be resolved to FileRepository and path argument will be passed into with specified value.

$container->bind(RepositoryInterface::class, FileRepository::class, ['path'=>'/data/storage']);

$controller = $container->make(Controller::class);

Binding parameters

You can bind parameters into the container fo resolving. It can be used as primitives binding or class binding:

// When FileRepository dependencies would be resolving, given value would be passed to `path` attribute.
$container->bindParameters(FileRepository::class, ['path' => '/data/storage']);

// When Controller would be resolved a FileRepository would be given as RepositoryInterface dependency.
$container->bindParameters(Controller::class, [RepositoryInterface::class => FileRepository::class]);

Singleton

The singleton method binds a class or interface into the container that should be resolved once. First time it will be resolved and stored in the container, so other times the same object instance will be returned on subsequent calls into the container.

$container->singleton(RepositoryInterface::class, FileRepository::class, ['path'=>'/data/storage']);

// Each time when RepositoryInterface needs to be resolved
// the same instance of FileRepository would be given.
$repository = $container->make(RepositoryInterface::class);

Alias

Alias is another name for resolving.

$container->singleton(RepositoryInterface::class, FileRepository::class, ['path'=>'/data/storage']);
$container->alias(RepositoryInterface::class, 'repo');

// This would return FileRepository instance.
$container->make('repo');

Instance

You can register any object or value into the container.

$container->instance('path', '/data/storage');
// '/data/storage' would be returned
$container->make('path');

$container->instance(RepositoryInterface::class, new FileRepository('/data/storage'));
// FileRepository would be returned
$container->make(RepositoryInterface::class);

Resolving

When resolving some name, you can pass parameters to make() function to attach it for resolving subject.

$container->bind(RepositoryInterface::class, FileRepository::class);
$container->make(RepositoryInterface::class, ['path'=>'/data/storage']);

Sequence of making subject

When resolving some subject, the container checks for registered aliases first, checks for registered instances and resolves using reflections.