IoC container - Dutch PHP Conference 2018

Did you know your IoC container can do a whole lot more than just constructor injection? Besides that it is actually packed with features. Inflectors, resolving callbacks, aliasing, method invocation to name a few. In this talk you will learn how to leverage the power of a great container and service providers to write better, loosely coupled code. Well designed code put together by your IoC container will make your applications SOLID, modular, lean and decoupled from the framework!

Transcript

1. IOC container @hannesvdvreken #dpc
2. Hi, my name is Hannes.
3. !
4. IoC Container
5. I O C
6. International O C
7. International Olympic C
8. International Olympic Committee
9. International Olympic Committee
10. IoC Container
11. IoC Container
12. WHAT IS IOC? IoC == Inversion of Control
13. WHAT IS IOC? class Service { public function __construct() { init(); } public function init() { $config = config(‘ftpsettings…’); $this->ftp = new FTP(…); } public function calculate(); }
14. WHAT IS IOC? $service = $container->get(Service::class); $service->calculate();
15. But first: Design patterns WHAT IS IOC?
16. class Service { public function init() { // setup FTP } public function calculate() { // Get stuff from FTP. // Do calculations. // Return result. } } WHAT IS IOC?
17. class Service { public function __construct(Ftp $ftp) { } public function calculate() { // Get stuff from FTP. // Do calculations. // Return result. } } WHAT IS IOC?
18. class Service { public function __construct(Ftp $ftp) { } public function calculate() { // Get stuff from FTP. // Add caching to prevent hitting FTP over and over again // Do calculations. // Return result. } } WHAT IS IOC?
19. class Service { public function __construct(Ftp $ftp) { } public function calculate() { // Get stuff from FTP. // Add caching to prevent hitting FTP over and over again // Log that FTP is accessed. // Do calculations. // Return result. } } WHAT IS IOC?
20. class Service { public function __construct(Ftp $ftp) { } public function calculate() { // Get stuff from FTP. // Add caching to prevent hitting FTP over and over again // Log that FTP is accessed. // Do calculations. // Return result. } } WHAT IS IOC?
21. class FtpStorage { public function __construct(Ftp $ftp) { $this->ftp = $ftp; } public function get($key) { // Get it. // Cache it. // Log it. // Return it. } } WHAT IS IOC?
22. class Service { public function __construct(FtpStorage $storage) {
 $this->storage = $storage; } public function calculate() { $value = $this->storage->get($key); return $calculate($value); } } WHAT IS IOC?
23. interface Storage { public function get($key); } WHAT IS IOC?
24. class FtpStorage implements Storage { public function __construct(Ftp $ftp) { $this->ftp = $ftp; } public function get($key) { … } } WHAT IS IOC?
25. class Service { public function __construct(Storage $storage) {
 $this->storage = $storage; } } WHAT IS IOC?
26. class CacheDecorator implements Storage { public function __construct(Cache $cache, Storage $wrapped) {…} public function get($key) { return $this->cache->remember($key, 60, function () { return $this->wrapped->get($key); }); } } WHAT IS IOC?
27. class LogDecorator implements Storage { public function __construct(LoggerInterface $log, Storage $wrapped) {…} public function get($key) { $this->log->info('Retrieved value for '.$key); return $this->wrapped->get($key); } } WHAT IS IOC?
28. class FtpStorage implements Storage { public function __construct(Ftp $ftp) { $this->ftp = $ftp; } public function get($key) { // Get it and return it. } } WHAT IS IOC?
29. FtpStorage Service depends on depends on Ftp WHAT IS IOC?
30. FtpStorage implements <interface> Storage Service depends on depends on Ftp WHAT IS IOC?
31. FtpStorage <interface> Storage CacheDecorator Service LogDecorator S3Storage WHAT IS IOC? implements depends on
32. WHAT IS IOC? FtpStorage Service depends on depends on Ftp FtpStorage implements <interface> Storage Service depends on depends on Ftp
33. new Service($ftp); WHAT IS IOC?
34. new Service( new CacheDecorator( $cache, new LogDecorator( $logger, new FtpStorage( new Ftp($settings) ) ) ) ); WHAT IS IOC?
35. $container->get(Service::class); 1) Make FtpStorage 2) Wrap it with LogDecorator 3) Wrap LogDecorator instance with CacheDecorator 4) New up Service with CacheDecorator instance. WHAT IS IOC?
36. Dependency inversion: Interface + implementation Dependency injection: Injecting `Storage` into `Service` Inversion of Control: The container builds your objects and calls them WHAT IS IOC?
37. Inversion of Control IoC container to the rescue WHAT IS IOC?
38. Let the IoC container help you with Composition WHAT IS IOC?
39. symfony/dependency-injection illuminate/container aura/di zendframework/zend-di pimple/pimple league/container … container-interop/container-interop psr/container (PSR-11) CONSTRUCTOR INJECTION
41. PSR-11 namespace Interop\Container; use Psr\Container\ContainerInterface as PsrContainer; interface ContainerInterface extends PsrContainer { … }
42. PSR-11 namespace Psr\Container; interface ContainerInterface { public function get($id); public function has($id); }
43. Automatic object resolution
44. // League $container = new Container(); $container->delegate(new ReflectionContainer()); $listener = $container->get(SendInvoice::class); CONSTRUCTOR INJECTION
45. Reflection CONSTRUCTOR INJECTION
46. class SendInvoice { public function __construct(Mailer $mailer) { $this->mailer = $mailer; } public function listen(InvoiceGeneratedEvent $event) { … } } CONSTRUCTOR INJECTION
47. Constructor injection CONSTRUCTOR INJECTION
48. (new \ReflectionClass($classname)) ->getConstructor() ->getParameters(); CONSTRUCTOR INJECTION
49. Recursively CONSTRUCTOR INJECTION
50. Auto wiring: - Symfony - Zend - Laravel - league/container - … CONSTRUCTOR INJECTION
51. But what if our code is SOLID… The container can’t construct interfaces? CONSTRUCTOR INJECTION
52. Helping the container (not standardized)
53. Situation 1: When <<interface>> is type hinted, resolve <<class>> instead REGISTRATION - BINDING
54. Solution: Aliasing. REGISTRATION - BINDING
55. $container->add(MailerInterface::class, function () { return $container->get(Mailer::class); }); REGISTRATION - BINDING
56. // Symfony $container->setAlias(MailerInterface::class, Mailer::class); // Laravel $container->alias(MailerInterface::class, Mailer::class); REGISTRATION - BINDING
57. Situation 2: When <<class>> has non-type hinted constructor arguments. REGISTRATION - BINDING
58. Solution: Define dependencies. REGISTRATION - BINDING
59. // League, et al. $container->add(Mailer::class, function () { return new Mailer($username, $password); }); REGISTRATION - BINDING
60. // Symfony $container->register(Mailer::class) ->addArgument($username) ->addArgument($password); REGISTRATION - BINDING
61. Situation 3: When <<class>> is type hinted, always return the exact same object. REGISTRATION - BINDING
62. Example: Global state in a - Translator (user’s locale) - Entity Manager - Event dispatcher REGISTRATION - BINDING
63. Solution: Sharing an instance. REGISTRATION - BINDING
64. // League $container->share(EntityManagerInterface::class, function () { … }); // Laravel $container->singleton(EntityManagerInterface::class, function () { … }); // Symfony $container->register()->setShared(true); REGISTRATION - BINDING
65. Situation 4: When different classes need a different object of the same interface. REGISTRATION - BINDING
66. class PhotosController { public function __construct(FilesystemInterface $photos) { } } class FilesController { public function __construct(FilesystemInterface $files) { } } REGISTRATION - BINDING
67. Solution: Contextual binding. REGISTRATION - BINDING
68. // Laravel $container ->when(PhotosController::class) ->needs(FilesystemInterface::class) ->give('fs.photos'); REGISTRATION - CONTEXTUAL BINDING
69. // Laravel $container->bind('fs.photos', function () {}); $container->bind('fs.files', function () {}); REGISTRATION - BINDING
70. // League $container->add('fs.photos', …); $container->add(PhotosController::class, function ( $fs = $container->get('fs.photos'); return new PhotosController($fs); }); REGISTRATION - BINDING
71. Situation 5: When resolving <<interface>>, do some setup. REGISTRATION - BINDING
72. Example 1: When resolving the EntityManager, register some ModelListeners. REGISTRATION - BINDING
73. Example 2: interface EnvironmentAware { public function setEnv($env); } trait EnvironmentAware { public function setEnv($env) { $this->env = $env; } } REGISTRATION - CONTAINER EVENTS
74. Solution: Container events / inflection / hooks / … REGISTRATION - BINDING
75. // League $container->inflector(EntityManager::class, function (EntityManager $em) { $em->getConfiguration() ->getEntityListenerResolver() ->register(new ModelListener()); } ); REGISTRATION - BINDING
76. // Laravel $container->resolving(function (EnvironmentAware $object) { $object->setEnv(getenv('APP_ENV')); }); REGISTRATION - CONTAINER EVENTS
77. Also useful for: - Quickly injecting stuff REGISTRATION - CONTAINER EVENTS
78. interface CommandBusAware trait CommandBusAware interface EventDispatcherAware trait EventDispatcherAware REGISTRATION - CONTAINER EVENTS
79. Also useful for: - Quickly injecting stuff REGISTRATION - CONTAINER EVENTS
80. Also useful for: - Quickly injecting stuff - Injecting soft dependencies REGISTRATION - CONTAINER EVENTS
81. $container—>resolving(function (Mailer $mailer) { $mailer->setQueueResolver(function () { return $container->make(Queue::class); }); ); REGISTRATION - CONTAINER EVENTS
82. Also useful for: - Quickly injecting stuff - Injecting soft dependencies REGISTRATION - CONTAINER EVENTS
83. Also useful for: - Quickly injecting stuff - Injecting soft dependencies - Setting configurable values REGISTRATION - CONTAINER EVENTS
84. $container->resolving(function (Validator) { $fileTypes = $container->get('config')->get(…) $validator->setAllowedFileTypes($fileTypes); ); REGISTRATION - CONTAINER EVENTS
85. Where to put all this? REGISTRATION
86. Symfony: - Configuration files - Factories REGISTRATION
87. container-interop/service-provider Similar: - league/container - illuminate/container REGISTRATION
88. Using a container
89. Retrieving objects CALLING THE CONTAINER
90. // Psr\Container\ContainerInterface $container->has('fs'); $container->get('fs'); CALLING THE CONTAINER
91. Retrieving objects, with arguments CALLING THE CONTAINER
92. // League $container->add('fs', function ($args) { // Use $args[0] to see what folder to use. }); $container->get('fs', ['images']); CALLING THE CONTAINER
93. // League $container->add('fs.images', function () { return $container->get('fs', ['images']); }); CALLING THE CONTAINER
94. Calling functions, with resolved params CALLING THE CONTAINER
95. // League & Laravel $container->call($closure); $container->call(function (Mailer $mailer) {}); $container->call([$listener, 'handle']); $container->call('Listener::handle'); CALLING THE CONTAINER
96. (new ReflectionFunction($callback)) ->getParameters(); CALLING THE CONTAINER
97. // Laravel $func = $container->wrap('Listener@handle'); $func(); CALLING THE CONTAINER
98. public function wrap($callback) { return function () { $this->call($callback); }; } CALLING THE CONTAINER
99. Tagging CALLING THE CONTAINER
100. Beware: Tagging in Symfony != Tagging in Laravel CALLING THE CONTAINER
101. // Laravel $container->tag('fs.images', 'filesystem'); $container->tag('fs.pdfs', 'filesystem'); $filesystems = $container->tagged('filesystem'); foreach ($filesystems as $filesystem) { … } CALLING THE CONTAINER
102. Preferably only in - Factories - Event Dispatchers - Router - Command Bus - … CALLING THE CONTAINER
103. Bonus
104. Solving circular dependencies BONUS - CIRCULAR DEPENDENCIES
105. $mailer = new Mailer(QueueInterface $queue); $queue = new Queue(MailerInterface $mailer); BONUS - CIRCULAR DEPENDENCIES
106. $mailer = new Mailer(); $queue = new Queue(MailerInterface $mailer); $mailer->setQueueResolver($callable); BONUS CIRCULAR DEPENDENCIES
107. $queue = $container->get(QueueInterface::class); // League $container->inflector(Mailer::class, function () { $mailer->setQueueResolver(function () { return $container->get(QueueInterface::class); }); }); BONUS CIRCULAR DEPENDENCIES
108. Environment aware injection $container->bind(‘fs.photos’::class, function () { if (getenv(‘APP_ENV’) === ‘integration’) { // Fill in memory adapter // with integration testing files
 } else { // Normal connection to S3. } }); BONUS - CIRCULAR DEPENDENCIES
109. recap: Reflection Aliasing Soft dependencies Using container
110. Thank you! @hannesvdvreken #dpc
111. Time for questions. @hannesvdvreken #dpc