Mastering Dependency Injection in D8

The Symfony Dependency Injection component is a centerpiece of D8 core. But did you know you could use it in your own modules? This talk will teach you about dependency injection as a design pattern. It will tell you how it is used in D8, and how you can leverage it for your own needs for coding custom pages/features. We will talk about the container, all kind of service configurations you can do, factories, decorators, configurators, etc. The promise? Decoupling your code to make it maintainable and testable over time. Let's see how a good component and a few best practices make it happen.

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1. #DrupalCon @nicolasgrekas Mastering Dependency Injection in D8
2. @nicolasgrekas #DrupalCon
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11. #DrupalCon @nicolasgrekas That's Dependency Injection... there is nothing more
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16. #DrupalCon @nicolasgrekas Constructor injection > Setter injection* >> Property injection** *~ok with circular dependencies, which should be avoided anyway **bad practice really
17. #DrupalCon @nicolasgrekas Dependency Injection... is like never writting “new” in your code* *except for data objects, e.g. new \DateTime();
18. #DrupalCon @nicolasgrekas Reusable Testable Pluggable Loosely coupled
19. #DrupalCon @nicolasgrekas SessionStorageInterface User $cookieName ArrayStorage RedisStorage SessionStorage RedisConnection $redisHost
20. #DrupalCon @nicolasgrekas Dependency Injection... implies recipes for wiring an object and its dependencies
21. #DrupalCon @nicolasgrekas The session? The logger?
22. #DrupalCon @nicolasgrekas Here comes the Dependency Injection Container
23. #DrupalCon @nicolasgrekas The DIC is an object that has all the recipes to instantiate “The” objects of your app, recursively
24. #DrupalCon @nicolasgrekas The DIC is an object that has all the recipes to instantiate the services of your app, recursively
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27. #DrupalCon @nicolasgrekas The simplest recipe
28. #DrupalCon @nicolasgrekas Adding a constructor argument
29. #DrupalCon @nicolasgrekas Doing setter injection
30. #DrupalCon @nicolasgrekas Using a factory
31. #DrupalCon @nicolasgrekas A factory service with arguments
32. #DrupalCon @nicolasgrekas Using a configurator* *quite rare in practice
33. #DrupalCon @nicolasgrekas New vs shared instance
34. #DrupalCon @nicolasgrekas Take a breath Let’s play with definitions now
35. #DrupalCon @nicolasgrekas Using aliases
36. #DrupalCon @nicolasgrekas With parameters
37. #DrupalCon @nicolasgrekas Abstract services
38. #DrupalCon @nicolasgrekas By decoration
39. #DrupalCon @nicolasgrekas By decoration
40. #DrupalCon @nicolasgrekas With tags
41. #DrupalCon @nicolasgrekas We’re almost done
42. #DrupalCon @nicolasgrekas The DIC is verified, built compiled, optimized, dumped, cached* *Tags, circular references, aliases, private inlined/removed, abstract removed, parameters resolved, etc.
43. #DrupalCon @nicolasgrekas Hey, it’s DrupalCon Dublin!
44. #DrupalCon @nicolasgrekas Let’s define our brewery service
45. #DrupalCon @nicolasgrekas And finally, our IrishBeerController
46. #DrupalCon @nicolasgrekas Pro-tips
47. #DrupalCon @nicolasgrekas Injecting the DIC itself is an anti-pattern called service locator/registry
48. #DrupalCon @nicolasgrekas Avoid circular dependencies when possible Use lazy or setter injection otherwise…
49. #DrupalCon @nicolasgrekas Services should be stateless, really aka reusable
50. #DrupalCon @nicolasgrekas The DIC is just a tool not The tool!
51. @nicolasgrekas #DrupalCon MERCI ! see you @SensioLabs’ booth