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IOC container @hannesvdvreken PHPCE

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Hi, my name is Hannes.

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!

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IoC Container

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I O C

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International O C

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International Olympic C

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International Olympic Committee

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International Olympic Committee

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WHAT IS IOC? IoC == Inversion of Control

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But first: Design patterns WHAT IS IOC?

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class Service { public function calculate() { // Get stuff from FTP. // Do calculations. // Return result. } } WHAT IS IOC?

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class Service { public function __construct(Ftp $ftp) { } public function calculate() { // Get stuff from FTP. // Do calculations. // Return result. } } WHAT IS IOC?

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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?

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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?

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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?

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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?

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class Service { public function __construct(FtpStorage $storage) {
 $this->storage = $storage; } } WHAT IS IOC?

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interface Storage { public function get($key); } WHAT IS IOC?

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class FtpStorage implements Storage { public function __construct(Ftp $ftp) { $this->ftp = $ftp; } public function get($key) { … } } WHAT IS IOC?

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class Service { public function __construct(Storage $storage) {
 $this->storage = $storage; } } WHAT IS IOC?

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class CacheDecorator implements Storage { public function __construct(Cache $cache, Storage $storage) {…} public function get($key) { return $this->cache->remember($key, 60, function () { return $this->storage->get($key); }); } } WHAT IS IOC?

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class LogDecorator implements Storage { public function __construct(LoggerInterface $log, Storage $storage) {…} public function get($key) { $this->log->info('Retrieved value for '.$key); return $this->storage->get($key); } } WHAT IS IOC?

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class FtpStorage implements Storage { public function __construct(Ftp $ftp) { $this->ftp = $ftp; } public function get($key) { // Get it and return it. } } WHAT IS IOC?

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Dependency inversion: Interface + implementation Dependency injection: Injecting `Storage` into `Service` Inversion of Control: The container builds your objects and calls them WHAT IS IOC?

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FtpStorage Service depends on depends on Ftp WHAT IS IOC?

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FtpStorage implements Storage Service depends on depends on Ftp WHAT IS IOC?

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FtpStorage Storage CacheDecorator Service LogDecorator S3Storage depends on WHAT IS IOC? implements

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new Service(new FtpStorage(new Ftp($settings))); WHAT IS IOC?

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Don’t create these instances yourself WHAT IS IOC?

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$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?

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Inversion of Control IoC container to the rescue WHAT IS IOC?

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IoC container is here to help you with Composition WHAT IS IOC?

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symfony/dependency-injection illuminate/container aura/di zendframework/zend-di pimple/pimple league/container … container-interop/container-interop psr/container (PSR-11) CONSTRUCTOR INJECTION

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CONSTRUCTOR INJECTION namespace Interop\Container; use Psr\Container\ContainerInterface as PsrContainer; interface ContainerInterface extends PsrContainer { … }

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Automatic object resolution

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class SendInvoice { public function __construct(Mailer $mailer) { $this->mailer = $mailer; } public function listen($event) { … } } CONSTRUCTOR INJECTION

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$listener = $container->get(SendInvoice::class); CONSTRUCTOR INJECTION

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Constructor injection CONSTRUCTOR INJECTION

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$listener = $container->get(SendInvoice::class); CONSTRUCTOR INJECTION

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// League $container = new Container(); $container->delegate(new ReflectionContainer()); $listener = $container->get(SendInvoice::class); CONSTRUCTOR INJECTION

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Reflection CONSTRUCTOR INJECTION

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(new \ReflectionClass($class)) ->getConstructor() ->getParameters(); CONSTRUCTOR INJECTION

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Recursively CONSTRUCTOR INJECTION

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class SendInvoice { public function __construct(Mailer $mailer) { $this->mailer = $mailer; } public function listen(InvoiceGeneratedEvent $event) { … } } CONSTRUCTOR INJECTION

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Auto wiring: - Symfony - Zend - Laravel - league/container - … CONSTRUCTOR INJECTION

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Helping the container

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Situation 1: When <> is type hinted, resolve <> instead REGISTRATION - BINDING

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Solution: Aliasing. REGISTRATION - BINDING

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// Symfony $container->setAlias(MailerInterface::class, Mailer::class); // Laravel $container->alias(MailerInterface::class, Mailer::class); // League, et al. $container->add(MailerInterface::class, function () { return $container->get(Mailer::class); }); REGISTRATION - BINDING

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Situation 2: When <> has non-type hinted constructor arguments. REGISTRATION - BINDING

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Solution: Define dependencies. REGISTRATION - BINDING

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// Symfony $container->register(Mailer::class) ->addArgument(…); REGISTRATION - BINDING

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// Pimple $container[MailerInterface::class] = function () { … }; REGISTRATION - BINDING

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Situation 3: When <> is type hinted, always return the same object. REGISTRATION - BINDING

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Example: Global state in a - Translator - View - Session REGISTRATION - BINDING

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Solution: Sharing an instance. REGISTRATION - BINDING

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// League $container->share(EntityManagerInterface::class, function () { … }); // Laravel $container->singleton(EntityManagerInterface::class, function () { … }); // Symfony $container->register()->setShared(true); REGISTRATION - BINDING

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Situation 4: When different classes need a different object of the same interface. REGISTRATION - BINDING

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Solution: Contextual binding. REGISTRATION - BINDING

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// Laravel $container->bind('fs.photos', function () {}); $container->bind('fs.files', function () {}); REGISTRATION - BINDING

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// Laravel $container ->when(PhotosController::class) ->needs(FilesystemInterface::class) ->give('fs.photos'); REGISTRATION - CONTEXTUAL BINDING

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Situation 5: When resolving <>, do some setup. REGISTRATION - BINDING

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Example: When resolving the EntityManager, register some ModelListeners. REGISTRATION - BINDING

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Solution: Container events / inflection / hooks / … REGISTRATION - BINDING

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// League $container->inflector(EntityManager, function ($em) $em->getConfiguration() ->getEntityListenerResolver() ->register(new ModelListener()); }); REGISTRATION - BINDING

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// Laravel $container->resolving(function (EntityManager $em) … }); REGISTRATION - BINDING

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interface EnvironmentAware { public function setEnv($env); } REGISTRATION - CONTAINER EVENTS

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trait EnvironmentAware { public function setEnv($env) { $this->env = $env; } private function isEnv($envs): bool { return in_array($this->env, (array) $envs); } } REGISTRATION - CONTAINER EVENTS

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$container->resolving(function (EnvironmentAware $object) { $object->setEnv(getenv(‘APP_ENV’)); }); REGISTRATION - CONTAINER EVENTS

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Also useful for: - Quickly injecting stuff REGISTRATION - CONTAINER EVENTS

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interface CommandBusAware trait CommandBusAware interface EventDispatcherAware trait EventDispatcherAware REGISTRATION - CONTAINER EVENTS

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Also useful for: - Quickly injecting stuff REGISTRATION - CONTAINER EVENTS

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Also useful for: - Quickly injecting stuff - Injecting soft dependencies REGISTRATION - CONTAINER EVENTS

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$this->app->resolving(function (Mailer $mailer) { $mailer->setQueueResolver(function () { return $this->app->make(Queue::class); }); ); REGISTRATION - CONTAINER EVENTS

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Also useful for: - Quickly injecting stuff - Injecting soft dependencies REGISTRATION - CONTAINER EVENTS

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Also useful for: - Quickly injecting stuff - Injecting soft dependencies - Setting configurable values REGISTRATION - CONTAINER EVENTS

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$this->app->resolving(function (Validator) { $fileTypes = $app['config']->get(…) $validator->setAllowedFileTypes($fileTypes); ); REGISTRATION - CONTAINER EVENTS

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Where to put all this? REGISTRATION

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container-interop/service-provider Similar to: - league/container - illuminate/container REGISTRATION

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Symfony: - Configuration files - Factories REGISTRATION

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Using a container

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Preferably only in - Factories - Event Dispatchers - Router - Command Bus - … CALLING THE CONTAINER

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Retrieving objects CALLING THE CONTAINER

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// Psr\Container\ContainerInterface $container->has('fs'); $container->get('fs'); CALLING THE CONTAINER

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Retrieving objects, with arguments CALLING THE CONTAINER

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// Laravel $container->bind('fs', function ($args) { // Use $args[0] to see what folder to use. }); $container->make('fs', ['images']); CALLING THE CONTAINER

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// Laravel $container->bind('fs.images', function () { return $container->make('fs', ['images']); }); CALLING THE CONTAINER

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Calling functions, with resolved params CALLING THE CONTAINER

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// League & Laravel $container->call($closure); $container->call(function (Mailer $mailer) {}); $container->call([$listener, 'handle']); $container->call('Listener::handle'); CALLING THE CONTAINER

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(new ReflectionFunction($callback)) ->getParameters(); CALLING THE CONTAINER

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// Laravel $func = $container->wrap('Listener@handle'); $func(); CALLING THE CONTAINER

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public function wrap($callback) { return function () { $this->call($callback); }; } CALLING THE CONTAINER

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Tagging CALLING THE CONTAINER

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// Laravel $container->tag('fs.images', 'filesystem'); $container->tag('fs.pdfs', 'filesystem'); $filesystems = $container->tagged('filesystem'); foreach ($filesystems as $filesystem) { … } CALLING THE CONTAINER

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Bonus

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Solving circular dependencies BONUS - CIRCULAR DEPENDENCIES

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$mailer = new Mailer(QueueInterface $queue); $queue = new Queue(MailerInterface $mailer); BONUS - CIRCULAR DEPENDENCIES

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$mailer = new Mailer(); $queue = new Queue(MailerInterface $mailer); $mailer->setQueueResolver($callable); BONUS CIRCULAR DEPENDENCIES

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$queue = $container->get(QueueInterface); // League $container->inflector(Mailer::class, function () { $mailer->setQueueResolver(function () use ($container) return $container->get(QueueInterface::class); }); }); BONUS CIRCULAR DEPENDENCIES

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recap: Reflection Binding Calling code Bonus

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@hannesvdvreken Thank you! PHPCE

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@hannesvdvreken Time for questions. PHPCE

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• http://mwl.be REFERENCES