Drupal Services & Dependency Injection

Drupal 11.x (applicable to Drupal 10.x+) | Philosophy: Services ARE configuration — defined in YAML, managed by the container

I need to...

I need to...	Guide	Summary
Understand what services and DI are	Services & DI Overview	When you need to understand the foundation of modern Drupal architecture — services provide reusable functionality, dependency injection eliminates hard-coded dependencies.
Learn how the service container works	Service Container Architecture	When you need to understand how Drupal's service container works under the hood — essential for debugging, optimization, and advanced patterns.
Understand the services.yml file structure	services.yml Schema	When you need to understand the structure of *.services.yml files — the foundational configuration format for Drupal services.
Know all available service definition properties	Service Definition Properties	When defining a service in *.services.yml — this reference catalog covers all available properties and their purposes.
Define a new service	Defining Services	When you need to register a new service with the Drupal container.
Use autowiring for my service	Autowiring	When you want the container to automatically resolve constructor arguments based on type hints — reduces YAML boilerplate for services with many dependencies.
Inject services into a controller or form	Constructor Injection	When injecting services into controllers, forms, or any class that implements ContainerInjectionInterface — the standard Drupal dependency injection pattern.
Inject services into a plugin (block, field formatter)	Plugin Injection	When injecting services into plugins (blocks, field formatters, field widgets, condition plugins, etc.) — plugins receive additional arguments (configuration, plugin_id, plugin_definition) that must be handled.
Decide when to use \Drupal vs dependency injection	The \Drupal Global Helper	When you understand when the \Drupal static helper is appropriate versus when dependency injection is required.
Tag a service (event_subscriber, cache.context, etc.)	Service Tags	When you need to mark a service for special processing by compiler passes — tags group services by purpose and enable extensible architectures.
Collect multiple tagged services	Tagged Service Collectors	When you need to build an extensible system where multiple services can register themselves to be used by a manager service — plugin-like architecture without the plugin API overhead.
Create an event subscriber	Event Subscribers	When you need to react to events in Drupal — kernel events (request, response, exception), entity events (CRUD operations), or custom events.
Alter existing services	Service Providers & Altering	When you need to alter existing service definitions, add new services programmatically, or register compiler passes — advanced container manipulation beyond YAML.
Add a compiler pass	Compiler Passes	When you need custom processing of service definitions during container compilation — validate services, process custom tags, or modify the container graph.
Find what core services are available	Core Services Reference	When you need to know what core services are available for injection — this catalog covers the most commonly used Drupal services.
Use a factory to create services	Factory Services	When a service requires complex instantiation logic, runtime parameters, or conditional creation — factories encapsulate creation logic.
Handle service serialization	DependencySerializationTrait	When your service or class is serialized (stored in cache, queued, etc.) and contains injected service dependencies — this trait prevents serializing the entire service object graph.
Learn DI best practices	Best Practices & Patterns	When you want to follow established Drupal community standards for services and dependency injection.
Avoid common mistakes	Anti-Patterns & Common Mistakes	When you want to avoid the most common mistakes developers make with Drupal services and dependency injection.
Understand security and performance	Security & Performance	When you need to understand the security and performance implications of service design and dependency injection patterns.
Find code references	Code Reference Map