Dependency Injection in PHP
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Slides from my talk during PHPCon Poland. Szczyrk 25/10/2013 More Domain-Driven Design related content at: https://domaincentric.net/
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Dependency Injection in PHP
- 1. Dependency Injection in PHP PHPCon Poland Szczyrk 25/10/13 ! by @cakper flickr.com/limowreck666/223731385/
- 2. Kacper Gunia // @cakper Software Engineer @SensioLabsUK Symfony Certified Developer #Symfony-PL // SymfonyLab.pl Silesian PHP User Group // SPUG.pl
- 3. Inversion of Control Dependency Injection Events Aspect Oriented Programming flickr.com/goetter/4559773791/
- 5. Dependency Injection ! ! class DvdPlayer { public function playDisc(Disc $disc) { echo 'Now playing: '.$disc-‐>getMovieTitle(); ! $tv = new Tv('Samsung 40"'); $tv-‐>sendToOutput($disc-‐>getResource()); } }
- 6. Dependency Injection class DvdPlayer { private $tv; ! public function __construct() { $this-‐>tv = new Tv('Samsung 40"');; } ! public function playDisc(Disc $disc) { echo 'Now playing: ' . $disc-‐>getMovieTitle(); $this-‐>tv-‐>sendToOutput($disc-‐>getResource()); } }
- 7. Dependency Injection class DvdPlayer { private $tv; ! public function __construct(Tv $tv) { $this-‐>tv = $tv; } // (...) } ! $tv = new Tv('Samsung 40"'); $dvdPlayer = new DvdPlayer($tv);
- 8. Dependency Injection class DvdPlayer { private $device; ! public function __construct(HdmiDevice $device) { $this-‐>device = $device; } // (...) } ! $projector = new Projector('Epson EB'); $dvdPlayer = new DvdPlayer($tv);
- 9. Nailed it!
- 10. “Dependency Injection is where components are given their dependencies through their constructors, methods, or directly into fields.” ! “(...) it is a 25-dollar term for a 5-cent concept” source: picocontainer.codehaus.org jamesshore.com
- 12. Constructor Injection class Tv implements HdmiDevice{} class DvdPlayer { private $device; ! public function __construct(HdmiDevice $device) { $this-‐>device = $device; } } ! $tv = new Tv('Samsung 40"'); $dvdPlayer = new DvdPlayer($tv);
- 13. Setter Injection class BlurayDisc implements Disc{} class DvdPlayer { private $disc; ! public function setDisc(Disc $disc) { $this-‐>disc = $disc; } } ! $disc = new BlurayDisc('Pulp Fiction'); $dvdPlayer = new DvdPlayer(); $dvdPlayer-‐>setDisc($disc);
- 14. Property Injection class DvdPlayer { public $remote; } ! $dvdPlayer = new DvdPlayer(); $dvdPlayer-‐>remote = ��new Remote();
- 15. Reflection Injection class DvdPlayer { private $powerSupply; } ! $dvdPlayer = new DvdPlayer(); $reflector = new ReflectionClass($dvdPlayer); $powerSupply = $reflector-‐>getProperty('powerSupply'); $powerSupply-‐>setAccessible(true); ! $powerSupply-‐>setValue($dvdPlayer, new PowerSupply());
- 27. “Dependency Injection Container is simply a PHP object that manages the instantiation of other objects” ! We call them “Services” source: symfony.com
- 28. Our DvdPlayer ! ! $tv = new Tv('Samsung 40"'); $dvdPlayer = new DvdPlayer($tv); ! $disc = new Disc('Pulp Fiction'); $dvdPlayer-‐>playDisc($disc);
- 29. Simple Container class class Container { public function getTv() { return new Tv('Samsung 40"'); } ! public function getDvdPlayer() { return new DvdPlayer($this-‐>getTv()); } }
- 30. Container use ! ! $container = new Container(); ! $dvdPlayer = $container-‐>getDvdPlayer(); ! $disc = new Disc('Pulp Fiction'); $dvdPlayer-‐>playDisc($disc);
- 32. DI & DIC Patterns flickr.com/thelearningcurvedotca/8645721482/
- 33. Pattern #1 Expect Interfaces, not Implementations flickr.com/deapeajay/2969264395/
- 34. Pattern #2 Don’t check null values flickr.com/g-ratphotos/3328593629/
- 35. class DvdPlayer { public $disc; ! public function play() { if (!is_null($this-‐>disc)) { $this-‐>sendToOutput($this-‐>disc-‐>getResource()); } } ! public function play() { if ($this-‐>disc instanceof Disc) { $this-‐>sendToOutput($this-‐>disc-‐>getResource()); } } }
- 36. Pattern #3 Avoid ‘Service Locator’ flickr.com/mateus27_24-25/2224073271/
- 37. class DvdPlayer { private $locator; ! public function __construct() { $this-‐>locator = ServiceLocator::getInstance(); } ! ! public function playDisc(Disc $disc) { $this-‐>locator -‐>getTv() -‐>sendToOutput($disc-‐>getResource()); } }
- 38. Pattern #4 Don’t inject whole container flickr.com/ucumari/580865728/
- 39. Pattern #5 In DIC store Services and Properties, but not Entities flickr.com/madlyinlovewithlife/8674850717/
- 40. Pattern #6 Don’t be afraid to create plenty of small Classes flickr.com/geoki/2691420977/
- 42. Services new Tv('Samsung 40”’) ! services: tv: class: Tv arguments: [“Samsung 40"”]
- 43. Parameters new Tv('Samsung 40”’) ! parameters: tv_name: Samsung 40"
- 44. Parameters & Services new Tv('Samsung 40”’) ! parameters: tv_name: Samsung 40" ! services: tv: class: Tv arguments: [“%tv_name%”] ! $container-‐>get('tv');
- 45. Compiled Container ! ! ! ! protected function getTvService() { return $this-‐>services['tv'] = new Tv('Samsung'); }
- 46. Static Factory services: tv class: Tv factory_class: TvFactory factory_method: get
- 47. Factory services: tv_factory: class: TvFactory tv class: Tv factory_service: tv_factory factory_method: get
- 48. Optional Dependencies class DvdPlayer { function __construct(HdmiDevice $device = null){} } ! services: tv: class: Tv arguments: [%tv_name%] dvd_player: class: DvdPlayer arguments ["@?tv"]
- 49. Lazy-loaded Services services: tv: class: Tv arguments: [“%tv_name%”] lazy: true
- 50. Private Services services: drm_decryptor: class: DrmDecryptor public: false dvd_player: class: DvdPlayer arguments [“@drm_decryptor”]
- 51. Scopes services: tv: class: Tv arguments: [“%tv_name%”] scope: prototype