Symfony Container

Transcript

1. Dependency Injection Dependency Injection Container (DIC)
2. The Problem
3. Error Notifier
4. Error Notifier Mailer Template Engine
5. Error Notifier Mailer Template Engine Swift Mailer Twig Environment
6. Pull Dependencies
7. public function notify($error) { $content = Mage::render(“error.twig”, $error); Mage::getMailer()->send( “everybody@ebay.com”, $content ); }
8. class Mage { public static function getMailer() { return new Mailer(); } public static function getSwiftMailer() { return new \Swift_Mailer(); } … }
9. Push Dependencies
10. public function notify($error) { $content = $this->template->render( “error.twig”, $error ); $this->mailer—>send( “everybody@ebay.com”, $content ); }
11. $swiftMailer = new \Swift_Mailer(); $mailer = new Mailer($swiftMailer); $twig = new \Twig_Environment(); $template = new Template\Engine($twig); $notifier = new Notifier($mailer, $template);
12. Pull vs Push
13. DI friendly code
14. Friendly Code • All dependencies MUST BE inside the service • Service SHOULD NOT be possible to instantiate without passing all compulsory dependencies • Services SHOULD NOT instantiate others services, they always have to be injected (except Builders, Factories and Service Container) • Services SHOULD NOT have circular dependencies
15. DON’T class Notifier { public function notify($error) { // Pull dependencies, depends on environment $_GLOBALS[‘mailer’]—>send($error->to, $error->text); } }
16. DO class Notifier { private $mailer; public function __construct(Mailer $mailer) { $this->mailer = $mailer; } public function notify($error) { // Explicit dependencies, depends on itself $this->mailer—>send($error->to, $error->text); } }
17. DON’T class Notifier { private $mailer; // Not guaranteed that method will be called public function setMailer(Mailer $mailer) { $this->mailer = $mailer; } public function notify($error) { $this->mailer—>send($error->to, $error->text); } }
18. DON’T class Notifier { … public function notify($error) { // Runtime is too late to know that dependency is not set if (!$this->mailer) { throw new \RuntimeException(‘Mailer is not injected :(’); } $this->mailer—>send($error->to, $error->text); } }
19. DO class Notifier { private $mailer; // Your code won’t run unless you pass all dependencies public function __construct(Mailer $mailer) { $this->mailer = $mailer; } public function notify($error) { $this->mailer—>send($error->to, $error->text); } }
20. DON’T class Notifier { private $mailer; public function __construct(\Swift_Mailer $swiftMailer) { // You loosing control on how Mailer instantiated // Redundant dependancy on Swift Mailer $this->mailer = new Mailer($swiftMailer); } public function notify($error) { $this->mailer—>send($error->to, $error->text); } }
21. DON’T class Notifier { private $mailer; public function __construct(Manager $mailManager) { // Redundant dependancy on Mail Manager $this->mailer = $mailerManager->createMailer(); } public function notify($error) { $this->mailer—>send($error->to, $error->text); } }
22. DO // Construct dependancy outside $mailer = new Mailer($swiftMailer); // Pass real dependancy instead of constructing // service inside the service $notifier = new Notifier($mailer);
23. Dependency Injection is about helping developers construct services without reading documentation or the code
24. Dependency Injection Container
25. Pimple (used in Silex)
26. $container = new Pimple(); $container[‘mailer’] = function($container) { return new Mailer($container[‘swift_mailer’]); }; $container[‘notifier’] = function($container) { return new Notifier( $container[‘mailer’], $container[‘template’] ); }; … $container[‘notifier’]->notify(new Error());
27. Symfony Service Container
28. notifier: class: Error\Notifier arguments: [@mailer, @template] mailer: class: Error\Mailer arguments: [@swift_mailer] swift_mailer: class: \Swift_Mailer template: class: Template\Engine arguments: [@twig]