Services & DI Container

1. # Services
2. # Application DI Container
3. # IoC Resolver
4. # Resolving

#Services

Services are helpful when you need to register a class with the IoC Container each time your site loads. For example, if you need a service for connecting to an external API like Stripe or Mailgun.

To create a service, use the make:service command.

php galaxy make:service MyService

Will create:

<?php  
namespace App\Services;  
  
use TypeRocket\Services\Service;  
  
class MyService extends Service  
{  
    protected $singleton = true;
    
    public function __construct()
    {
		// Runs when service is loaded into the container
		// this happens on every page load.
	}

	public function register() : Service  
	{  
	    // Runs when first instance is created
	    // this happens only when requested
	    return $this; 
	}
}

Then register the service to your app.services config file.

/*  
|--------------------------------------------------------------------------  
| Services  
|--------------------------------------------------------------------------  
|  
| Services you want loaded into the container as singletons.  
|  
*/  
'services' => [
    '\App\Services\AuthService',
    '\App\Services\MyService',  
],

You can then access the service instance using tr_service('MyService'). If your service is outside the App\Services namespace, use the tr_container() function and pass the full class name.

#Application DI Container

Register a class to the DI Container.

// singlton and alias are both optional arguments
$singleton = true;
$alias = 'my.class';

\TypeRocket\Core\Container::register(\MyNamespace\MyClass::class, function () {
    $api_key = 'sdfjd83mvbfy92kf';

    return new \MyNamespace\MyClass($api_key);
}, $singleton, $alias);

Get an instance from the DI container.

// by class name
$obj = \TypeRocket\Core\Container::resolve(\MyNamespace\MyClass::class);

// by alias
$obj = \TypeRocket\Core\Container::resolve('my.class');

Using helper.

$obj = tr_container(\MyNamespace\MyClass::class);

#IoC Resolver

The inversion of control resolver automatically tries to instantiate a class with its dependencies. The Resolver object will look at a class' constructor and automatically inject its dependencies.

#Resolving

The Resolver classes method resolve() take one argument:

1. $class - The name of the class.

The resolve() method will check the class' constructor and try to resolve the dependencies by looking at the type hints in the constructor. If a constructor argument has a default value and no type-hint the default value will be used.

// Classes
class Cheese {
    public $type;

    function __construct( $type = 'cheddar' ) {
        $this->type = $type;
    }
}

class Pizza {
    public $cheese;

    function __construct( \Cheese $cheese ) {
        $this->cheese = $cheese;
    }
}

// Resolver
$resolver = new \TypeRocket\Core\Resolver();
$pizza = $resolver->resolve('Pizza');
echo $pizza->cheese->type;

Will output,

cheddar