Revision: Thu, 28 May 2020 13:49:47 GMT

Framework - Container and Factories

The framework includes a set of interfaces and components intended to simplify dependency injection and object construction in your application.

Container implementation is fully compatible with PSR-11 Container.

PSR-11 Container

You can always access the container directly in your code by requesting Psr\Container\ContainerInterface:

use Psr\Container\ContainerInterface;

class HomeContoller
{
    public function index(ContainerInterface $container)
    {
        dump($container->get(App\App::class));
    }
}

Dependency Injection

Spiral support both method and constructor injections for your classes:

class UserMailer
{
    protected $mailer = null;

    public function __construct(Mailer $mailer)
    {
        $this->mailer = $mailer;
    }

    public function do()
    {
        $this->mailer->sendMail(...);
    }
}

The Mailer dependency will be automatically delivered by the container (auto-wiring).

Note, your controllers, commands, and jobs support method injection.

Configuring Container

You can configure container by creating a set of bindings between aliases or interfaces to concrete implementations.
Use Bootloaders to define bindings.

We can either use Spiral\Core\BinderInterface or Spiral\Core\Container to configure the application container.

To bind interface to concrete implementation:

public function boot(Container $container)
{
    $container->bind(MyInterface::class, MyImplementation::class);
}

To bind singleton:

public function boot(Container $container)
{
    $container->bindSingleton(MyImplementation::class, MyImplementation::class);
}

To bind with specific parameters:

public function boot(Container $container)
{
    $container->bindSingleton(MyImplementation::class, bind(MyImplementation::class, [
        'param' => 'value'
    ]));
}

Read about Config Objects to see how to manage config dependencies.

You can also use closure to configure your class automatically:

public function boot(Container $container)
{
    $container->bindSingleton(MyImplementation::class, function() {
        return new MyImplementation('some-value');
    });
}

Closures also support dependencies:

public function boot(Container $container)
{
    $container->bindSingleton(MyImplementation::class, function(SomeClass $class) {
        return new MyImplementation($class);
    });
}

To check if container has binding use:

dump($container->has(MyImplementation::class));

To remove the container binding:

$container->removeBinding(MyService::class);

Lazy Singletons

You can skip singleton binding by implementing Spiral\Core\Container\SingletonInterface in your class:

use Spiral\Core\Container\SingletonInterface;

class MyService implements SingletonInterface
{
    public function method()
    {
        //...
    }
}

Now, the container will automatically treat this class as a singleton in your application:

protected function index(MyService $service)
{
    dump($this->container->get(MyService::class) === $service);
}

FactoryInterface

In some cases, you might want to construct a desired class without resolving all of it's __constructor dependencies. You can use Spiral\Core\FactoryInterface for that purpose:

public function makeClass(FactoryInterface $factory)
{
    return $factory->make(MyClass::class, [
        'parameter' => 'value'
        // other dependencies will be resolved automatically
    ]); 
}

ResolverInterface

If you want to resolve method arguments to dynamic target (i.e., controller method) use Spiral\Core\ResolverInterface:

abstract class Handler
{
    /** @var ResolverInterface */
    protected $resolver;

    public function __construct(ResolverInterface $resolver)
    {
        $this->resolver = $resolver;
    }

    public function run(array $params)
    {
        $method = new \ReflectionMethod($this, 'do'); // the method to invoke with method injection
        $method->setAccessible(true);

        return $method->invokeArgs(
            $this, 
            $this->resolver->resolveArguments($method, $params) // resolve missing arguments
        );
    }
}

Method do now can request method injection:

class MyHandler extends Handler
{
    public function do(SomeClass $some)
    {
        // ...    
    }
}

Auto Wiring

Spiral Framework attempts to hide the container implementation and configuration from your domain layer by providing rich auto-wiring functionality. Though auto-wiring rules are straightforward, it's essential to learn them to avoid framework misbehavior.

Automatic Dependency Resolution

Framework container can automatically resolve the constructor or method dependencies by providing instances of concrete classes.

class MyController
{
    public function __construct(OtherClass $class, SomeInterface $some)
    {
    }
}

In a provided example, the container will attempt to give the instance of OtherClass by automatically constructing it. However, SomeInterface would not be resolved unless you have the proper binding in your container.

$container->bind(SomeInterface::class, SomeClass::class); 

Please note, the container will try to resolve all constructor dependencies (unless you manually provide some values). It means that all class dependencies must be available, or parameter must be declared as optional:

// will fail if `value` dependency not provided
__construct(OtherClass $class, $value)

// will use `null` as `value` if no other value provided
__construct(OtherClass $class, $value = null) 

// will fail if SomeInterface does not point to the concrete implemenation
__construct(OtherClass $class, SomeInterface $some) 

// will use null as value of `some` if no conrete implemation is provided
__construct(OtherClass $class, SomeInterface $some = null) 

Contextual Auto Wiring

In addition to regular method injections, the container can resolve the injection context automatically. Such a technique provides us the ability to request multiple databases using the following statement:

protected function index(Database $primary, Database $secondary)
{
    dump($primary);
    dump($secondary);
}

Where primary and secondary are database names.

Implement Spiral\Core\Container\InjectorInterface to create injection factory:

Now we have to define class responsible for such injections:

class Injector implements InjectorInterface
{
    public function createInjection(\ReflectionClass $class, string $context = null)
    {
        return new MyClass($context);
    }
}

Where MyClass is:

class MyClass 
{
    public function __construct(string $name)
    {
        //...
    }
}

Make sure to register inject in the container:

$container->bindInjector(MyClass::class, Injector::class);

As result we can request instance of MyClass using method arguments:

public function method(MyClass $john, MyClass $bob)
{
    dump($john);
    dump($bob);
}

You can always bypass contextual injection in Spiral\Core\FactoryInterface:

dump($factory->make(MyClass::class, ['name' => 'abc']));

Singletons

A lot of internal application services reside in a memory in the form of singleton objects. Such objects do not implement static getInstance, but rather configured to remain in container between requests.

Declaring your service or controller as a singleton is the shortest path to get small performance improvement, however, some rules must be applied to avoid memory and state leaks.

Define the Singleton

The framework provides multiple ways to declare a class object as a singleton. At first, you can create Bootloader in which you can bind class under its name:

class ServiceBootloader extends Bootloader
{
    protected const SIGNLETONS = [
        Service::class => Service::class
    ];
}

Now, you will always receive the same instance from the IoC container by doing the injection.

The alternative approach does not require Bootloader and can be defined via class itself, implement interface Spiral\Core\Container\SingletonInterface to declare to the container that class must be constructed only once:

use Spiral\Core\Container\SingletonInterface;

class Service implements SingletonInterface
{
    // ...
}

You can implement a singleton interface in services, controllers, middleware, etc. Do not implement it in Repositories and mappers as these classes state are managed by ORM.

Limitations

By keeping your services in memory between requests, you can avoid doing some complex initializations and computations over and over. However, you must remember that your services must be designed in stateless fashion and do not contain any user data.

You can not:

  • store user information in your singleton
  • store reference to PSR-7 request (use InputManager instead)
  • store reference to session (use SessionScope instead)
  • store RBAC actor (use GuardScope instead)

Pre-Heating

You are allowed to store data in services that can not change between user requests. For example, if you application relies on heavy XML as configuration source:

class Service implements SingletonService 
{
    private $configCache;

    public function getConfig(): array
    {
        if ($this->configCache !== null) {
            return $this->configCache;
        }

        $this->configCache = $this->readConfig(); // heavy operation

        return $this->configCache;
    }
}   

Using such an approach, you can perform complex computations only once and rely on RAM cache on later user requests.

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