Container Laravel Package

Getting Started

Minimal Steps

1. Installation:

   composer require league/container
   

   Requires PHP 8.3+ (as per latest release).

2. Basic Setup:

   use League\Container\Container;
   
   $container = new Container();
   

3. First Use Case: Register a service and resolve it:

   $container->add(\App\Services\MyService::class);
   $service = $container->get(\App\Services\MyService::class);
   

Where to Look First

• Basic Usage in the docs for core concepts.
• PSR-11 compliance ensures interoperability with other containers.
• Laravel Integration: Useful for lightweight DI outside Laravel’s built-in container (e.g., in CLI commands, tests, or microservices).

Implementation Patterns

Core Workflows

1. Constructor Injection:

   $container->add(\App\Services\UserService::class)
              ->addArgument(\App\Repositories\UserRepository::class);
   

2. Alias-Based Resolution (for interfaces/contracts):

   $container->add(\App\Contracts\UserRepository::class, \App\Repositories\MySqlUserRepository::class);
   $container->add(\App\Services\UserService::class)
              ->addArgument(\App\Contracts\UserRepository::class);
   

3. Service Providers (for modular registration):

   $container->addServiceProvider(new \App\Providers\AppServiceProvider());
   

   Define a provider with register() method to batch-add services.

4. Delegate Containers (fallback resolution):

   $fallback = new \League\Container\Container();
   $container->delegate($fallback);
   

Integration Tips

• Laravel Compatibility: Use alongside Laravel’s container (e.g., for CLI tasks):

  $container = new \League\Container\Container();
  $container->addServiceProvider(new \Illuminate\Foundation\ApplicationServiceProvider(app()));
  

• Testing: Mock dependencies easily:

  $container->add(\App\Services\PaymentService::class, new \App\Mocks\MockPaymentService());
  

• Performance: Pre-resolve expensive services:

  $container->add(\App\Services\CacheService::class, fn() => new \App\Services\RedisCacheService());
  

Gotchas and Tips

Pitfalls

1. Circular Dependencies: League’s container throws League\Container\Exception\NotFoundException for unresolvable services. Debug by checking registration order or using ->has() to verify availability.

2. Argument Resolution Overhead: Avoid ambiguous strings (e.g., "User"). Use explicit types or aliases:

   // Bad: Ambiguous
   $container->add(\App\Services\UserService::class)->addArgument("User");
   
   // Good: Explicit
   $container->add(\App\Services\UserService::class)->addArgument(\App\Models\User::class);
   

3. Service Provider Lifecycle: Providers are registered but not automatically invoked. Call register() manually or use addServiceProvider() with a provider that auto-registers.

4. Closure Caching: Closure-based services (e.g., ->add(\App\Service::class, fn() => new \App\Service())) are not cached by default. Use ->share() to enable singleton behavior:

   $container->share(\App\Services\ConfigService::class, fn() => new \App\Services\ConfigService());
   

Debugging Tips

• Check Registration:

  if (!$container->has(\App\Service::class)) {
      throw new \RuntimeException("Service not registered!");
  }
  

• Inspect Dependencies: Use ->getArguments() to see what’s being injected:

  $definition = $container->getDefinition(\App\Service::class);
  print_r($definition->getArguments());
  

• Delegate Debugging: Verify delegate order with ->getDelegates(). Delegates are checked in registration order.

Extension Points

1. Custom Argument Types: Extend League\Container\Argument\ArgumentInterface for domain-specific logic (e.g., environment variables):

   $container->addArgument(new \App\Arguments\EnvVarArgument('APP_DEBUG'));
   

2. Inflectors: Modify resolved objects post-instantiation:

   $container->addInflector(new \League\Container\Inflector\Inflector(
       fn($obj) => $obj->setLogger($container->get(\Psr\Log\LoggerInterface::class))
   ));
   

3. Event System: Listen for League\Container\Events\Building to intercept resolution:

   $container->on('building', fn($event) => $event->setValue(new \App\Mocks\MockService()));