Setting interface in the constructor gives InvalidDefinition error

[dingo-d]

I'm trying to use php-di in my WordPress plugin. In my plugin class I have tried with

class Plugin {
    public function register() : void {
      add_action( 'plugins_loaded', [ $this, 'register_services' ] );
    }

  public function register_services() {
    $container = new \DI\Container();

    $this->services = array_map(
      function( $class ) use ( $container ) {
        return $container->get( $class );
      },
      $this->get_service_classes()
    );

    array_walk(
      $this->services,
      function( $class ) {
        $class->register();
      }
    );
  }
}

In my main plugin file I'm calling the (new Plugin())->register() method via plugin factory to kickstart it all.

The get_service_classes method returns array of classes that need to be instantiated and autowired. For instance:

private function get_service_classes() : array {
    return [
      My_Plugin\Admin\Admin_View::class,
      // ...
    ];
}

In one example I have

final class Admin_View implements Service {
  private $plugin_options;

  public function __construct( Plugin_Options $plugin_options ) {
    $this->plugin_options = $plugin_options;
  }
}

This works because I'm passing the exact class Plugin_Options as the constructor type hint (I've set the use My_Plugin\Options\Plugin_Options above the class definition).

But, this also tightly couples my code, because I'm depending on concretes not abstracts (interface).

So, since my Plugin_Options class implements the same Service interface as 99.8% of my classes (service interface only has one public method register for registering hooks in WordPress), I tried to type hint against the Service interface

final class Admin_View implements Service {
  private $plugin_options;

  public function __construct( Service $plugin_options ) {
    $this->plugin_options = $plugin_options;
  }
}

This threw an error:

[09-May-2019 13:35:01 UTC] PHP Fatal error: Uncaught DI\Definition\Exception\InvalidDefinition: Entry "My_Plugin\Admin\Admin_View" cannot be resolved: Entry "My_Plugin\Core\Service" cannot be resolved: the class is not instantiable
Full definition:
Object (
class = #NOT INSTANTIABLE# My_Plugin\Core\Service
lazy = false
)
Full definition:
Object (
class = My_Plugin\Admin\Admin_View
lazy = false
__construct(
$plugin_options = get(My_Plugin\Core\Service)
)
) in /public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Definition/Exception/InvalidDefinition.php:18
Stack trace:
#0 /public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Definition/Resolver/ObjectCreator.php(155): DI\Definition\Exception\InvalidDefinition::create(Object(DI\Definition\ObjectDefinition), 'Entry "My_Plugi...')
#1 /public_html/wp-content/plugins/my-plugin/vend in /public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Definition/Exception/InvalidDefinition.php on line 18

The issue is that Service is an interface.

I've tried by defining the ContainerBuilder

public function register_services() {
    // Implement PHP-DI.
    $builder = new ContainerBuilder();

    $builder->addDefinitions(
      [
        Service::class => \DI\autowire( OldAdmin\Admin_View::class ),
      ]
    );

    $container = $builder->build();
    //...
}

But that caused circular definitions error.

[09-May-2019 14:30:31 UTC] PHP Fatal error: Uncaught DI\DependencyException: Circular dependency detected while trying to resolve entry 'My_Plugin\Core\Service' in public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Container.php:371
Stack trace:
#0 public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Container.php(137): DI\Container->resolveDefinition(Object(DI\Definition\AutowireDefinition))
#1 public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Definition/Reference.php(53): DI\Container->get('Developer_Porta...')
#2 public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Definition/Resolver/ResolverDispatcher.php(59): DI\Definition\Reference->resolve(Object(DI\Container))
#3 public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Definition/Resolver/ParameterResolver in public_html/wp-content/plugins/my-plugin/vendor/php-di/php-di/src/Container.php on line 371

Is the problem that I'm using the same interface in most places? Should I create separate interface and then pass this one (even thought that interface may just implement the Service interface)?
Or am I doing something wrong completely? I've read the documentation but had no luck so far :/

Additional info

PHP Version: 7.2.14
php-di Version: 6.0.8

[SvenRtbg]

Your Admin_View implements Service and requires Service as a constructor parameter that is implemented by Admin_View?

How would you try to resolve this manually?
$admin_view = new Admin_View(new Admin_View(new Admin_View(...)));

I'd suggest that you try to write code without PHP-DI that resolves your class injection manually for one case first. That way you'll easily find why you are unintentionally creating circles. As a result you'll be able to create the interfaces and classes properly, and PHP-DI will work then.

[dingo-d]

Yeah, I've tried to resolve this issue for a couple of hours without luck. I guess I'll have to rewrite the Plugin_Options class so that I can inject it properly in the Admin_View class.

I'm doing a refactor of an old code I wrote and I'm trying to write everything with proper OOP. That's why I'm looking into a DI container, to make my life a bit easier. Both of those classes are not refactored (yet) 😬

Well back to the drawing board for me 😅