Mastering Dependency Injection in D8

Slide 1

Slide 1 text

#DrupalCon @nicolasgrekas Mastering Dependency Injection in D8

Slide 2

Slide 2 text

@nicolasgrekas #DrupalCon

Slide 3

Slide 3 text

#DrupalCon @nicolasgrekas

Slide 4

Slide 4 text

#DrupalCon @nicolasgrekas

Slide 5

Slide 5 text

#DrupalCon @nicolasgrekas

Slide 6

Slide 6 text

#DrupalCon @nicolasgrekas

Slide 7

Slide 7 text

#DrupalCon @nicolasgrekas

Slide 8

Slide 8 text

#DrupalCon @nicolasgrekas

Slide 9

Slide 9 text

#DrupalCon @nicolasgrekas

Slide 10

Slide 10 text

#DrupalCon @nicolasgrekas

Slide 11

Slide 11 text

#DrupalCon @nicolasgrekas That's Dependency Injection... there is nothing more

Slide 12

Slide 12 text

#DrupalCon @nicolasgrekas

Slide 13

Slide 13 text

#DrupalCon @nicolasgrekas

Slide 14

Slide 14 text

#DrupalCon @nicolasgrekas

Slide 15

Slide 15 text

#DrupalCon @nicolasgrekas

Slide 16

Slide 16 text

#DrupalCon @nicolasgrekas Constructor injection > Setter injection* >> Property injection** *~ok with circular dependencies, which should be avoided anyway **bad practice really

Slide 17

Slide 17 text

#DrupalCon @nicolasgrekas Dependency Injection... is like never writting “new” in your code* *except for data objects, e.g. new \DateTime();

Slide 18

Slide 18 text

#DrupalCon @nicolasgrekas Reusable Testable Pluggable Loosely coupled

Slide 19

Slide 19 text

#DrupalCon @nicolasgrekas SessionStorageInterface User $cookieName ArrayStorage RedisStorage SessionStorage RedisConnection $redisHost

Slide 20

Slide 20 text

#DrupalCon @nicolasgrekas Dependency Injection... implies recipes for wiring an object and its dependencies

Slide 21

Slide 21 text

#DrupalCon @nicolasgrekas The session? The logger?

Slide 22

Slide 22 text

#DrupalCon @nicolasgrekas Here comes the Dependency Injection Container

Slide 23

Slide 23 text

#DrupalCon @nicolasgrekas The DIC is an object that has all the recipes to instantiate “The” objects of your app, recursively

Slide 24

Slide 24 text

#DrupalCon @nicolasgrekas The DIC is an object that has all the recipes to instantiate the services of your app, recursively

Slide 25

Slide 25 text

#DrupalCon @nicolasgrekas

Slide 26

Slide 26 text

#DrupalCon @nicolasgrekas

Slide 27

Slide 27 text

#DrupalCon @nicolasgrekas The simplest recipe

Slide 28

Slide 28 text

#DrupalCon @nicolasgrekas Adding a constructor argument

Slide 29

Slide 29 text

#DrupalCon @nicolasgrekas Doing setter injection

Slide 30

Slide 30 text

#DrupalCon @nicolasgrekas Using a factory

Slide 31

Slide 31 text

#DrupalCon @nicolasgrekas A factory service with arguments

Slide 32

Slide 32 text

#DrupalCon @nicolasgrekas Using a configurator* *quite rare in practice

Slide 33

Slide 33 text

#DrupalCon @nicolasgrekas New vs shared instance

Slide 34

Slide 34 text

#DrupalCon @nicolasgrekas Take a breath Let’s play with definitions now

Slide 35

Slide 35 text

#DrupalCon @nicolasgrekas Using aliases

Slide 36

Slide 36 text

#DrupalCon @nicolasgrekas With parameters

Slide 37

Slide 37 text

#DrupalCon @nicolasgrekas Abstract services

Slide 38

Slide 38 text

#DrupalCon @nicolasgrekas By decoration

Slide 39

Slide 39 text

#DrupalCon @nicolasgrekas By decoration

Slide 40

Slide 40 text

#DrupalCon @nicolasgrekas With tags

Slide 41

Slide 41 text

#DrupalCon @nicolasgrekas We’re almost done

Slide 42

Slide 42 text

#DrupalCon @nicolasgrekas The DIC is verified, built compiled, optimized, dumped, cached* *Tags, circular references, aliases, private inlined/removed, abstract removed, parameters resolved, etc.

Slide 43

Slide 43 text

#DrupalCon @nicolasgrekas Hey, it’s DrupalCon Dublin!

Slide 44

Slide 44 text

#DrupalCon @nicolasgrekas Let’s define our brewery service

Slide 45

Slide 45 text

#DrupalCon @nicolasgrekas And finally, our IrishBeerController

Slide 46

Slide 46 text

#DrupalCon @nicolasgrekas Pro-tips

Slide 47

Slide 47 text

#DrupalCon @nicolasgrekas Injecting the DIC itself is an anti-pattern called service locator/registry

Slide 48

Slide 48 text

#DrupalCon @nicolasgrekas Avoid circular dependencies when possible Use lazy or setter injection otherwise…