PHP 中介者模式讲解和代码示例

<?php namespace RefactoringGuru\Mediator\RealWorld; /** * The Event Dispatcher class acts as a Mediator and contains the subscription * and notification logic. While a classic Mediator often depends on concrete * component classes, this one is only tied to their abstract interfaces. * * We are able to achieve this level of indirection thanks to the way the * connections between components are established. The components themselves may * subscribe to specific events that they are interested in via the Mediator's * subscription interface. * * Note, we can't use the PHP's built-in Subject/Observer interfaces here * because we'll be stretching them too far from what they were designed for. */ class EventDispatcher { /** * @var array */ private $observers = []; public function __construct() { // The special event group for observers that want to listen to all // events. $this->observers["*"] = []; } private function initEventGroup(string &$event = "*"): void { if (!isset($this->observers[$event])) { $this->observers[$event] = []; } } private function getEventObservers(string $event = "*"): array { $this->initEventGroup($event); $group = $this->observers[$event]; $all = $this->observers["*"]; return array_merge($group, $all); } public function attach(Observer $observer, string $event = "*"): void { $this->initEventGroup($event); $this->observers[$event][] = $observer; } public function detach(Observer $observer, string $event = "*"): void { foreach ($this->getEventObservers($event) as $key => $s) { if ($s === $observer) { unset($this->observers[$event][$key]); } } } public function trigger(string $event, object $emitter, $data = null): void { echo "EventDispatcher: Broadcasting the '$event' event.\n"; foreach ($this->getEventObservers($event) as $observer) { $observer->update($event, $emitter, $data); } } } /** * A simple helper function to provide global access to the event dispatcher. */ function events(): EventDispatcher { static $eventDispatcher; if (!$eventDispatcher) { $eventDispatcher = new EventDispatcher(); } return $eventDispatcher; } /** * The Observer interface defines how components receive the event * notifications. */ interface Observer { public function update(string $event, object $emitter, $data = null); } /** * Unlike our Observer pattern example, this example makes the UserRepository * act as a regular component that doesn't have any special event-related * methods. Like any other component, this class relies on the EventDispatcher * to broadcast its events and listen for the other ones. * * @see \RefactoringGuru\Observer\RealWorld\UserRepository */ class UserRepository implements Observer { /** * @var array List of application's users. */ private $users = []; /** * Components can subscribe to events by themselves or by client code. */ public function __construct() { events()->attach($this, "users:deleted"); } /** * Components can decide whether they'd like to process an event using its * name, emitter or any contextual data passed along with the event. */ public function update(string $event, object $emitter, $data = null): void { switch ($event) { case "users:deleted": if ($emitter === $this) { return; } $this->deleteUser($data, true); break; } } // These methods represent the business logic of the class. public function initialize(string $filename): void { echo "UserRepository: Loading user records from a file.\n"; // ... events()->trigger("users:init", $this, $filename); } public function createUser(array $data, bool $silent = false): User { echo "UserRepository: Creating a user.\n"; $user = new User(); $user->update($data); $id = bin2hex(openssl_random_pseudo_bytes(16)); $user->update(["id" => $id]); $this->users[$id] = $user; if (!$silent) { events()->trigger("users:created", $this, $user); } return $user; } public function updateUser(User $user, array $data, bool $silent = false): ?User { echo "UserRepository: Updating a user.\n"; $id = $user->attributes["id"]; if (!isset($this->users[$id])) { return null; } $user = $this->users[$id]; $user->update($data); if (!$silent) { events()->trigger("users:updated", $this, $user); } return $user; } public function deleteUser(User $user, bool $silent = false): void { echo "UserRepository: Deleting a user.\n"; $id = $user->attributes["id"]; if (!isset($this->users[$id])) { return; } unset($this->users[$id]); if (!$silent) { events()->trigger("users:deleted", $this, $user); } } } /** * Let's keep the User class trivial since it's not the focus of our example. */ class User { public $attributes = []; public function update($data): void { $this->attributes = array_merge($this->attributes, $data); } /** * All objects can trigger events. */ public function delete(): void { echo "User: I can now delete myself without worrying about the repository.\n"; events()->trigger("users:deleted", $this, $this); } } /** * This Concrete Component logs any events it's subscribed to. */ class Logger implements Observer { private $filename; public function __construct($filename) { $this->filename = $filename; if (file_exists($this->filename)) { unlink($this->filename); } } public function update(string $event, object $emitter, $data = null) { $entry = date("Y-m-d H:i:s") . ": '$event' with data '" . json_encode($data) . "'\n"; file_put_contents($this->filename, $entry, FILE_APPEND); echo "Logger: I've written '$event' entry to the log.\n"; } } /** * This Concrete Component sends initial instructions to new users. The client * is responsible for attaching this component to a proper user creation event. */ class OnboardingNotification implements Observer { private $adminEmail; public function __construct(string $adminEmail) { $this->adminEmail = $adminEmail; } public function update(string $event, object $emitter, $data = null): void { // mail($this->adminEmail, // "Onboarding required", // "We have a new user. Here's his info: " .json_encode($data)); echo "OnboardingNotification: The notification has been emailed!\n"; } } /** * The client code. */ $repository = new UserRepository(); events()->attach($repository, "facebook:update"); $logger = new Logger(__DIR__ . "/log.txt"); events()->attach($logger, "*"); $onboarding = new OnboardingNotification("1@example.com"); events()->attach($onboarding, "users:created"); // ... $repository->initialize(__DIR__ . "users.csv"); // ... $user = $repository->createUser([ "name" => "John Smith", "email" => "john99@example.com", ]); // ... $user->delete(); 

UserRepository: Loading user records from a file. EventDispatcher: Broadcasting the 'users:init' event. Logger: I've written 'users:init' entry to the log. UserRepository: Creating a user. EventDispatcher: Broadcasting the 'users:created' event. OnboardingNotification: The notification has been emailed! Logger: I've written 'users:created' entry to the log. User: I can now delete myself without worrying about the repository. EventDispatcher: Broadcasting the 'users:deleted' event. UserRepository: Deleting a user. Logger: I've written 'users:deleted' entry to the log.