4 真实案例

<?php
/**
 * The UserRepository represents a Subject. Various objects are interested in
 * tracking its internal state, whether it's adding a new user or removing one.
 */
class UserRepository implements \SplSubject
{
    /**
     * @var array The list of users.
     */
    private $users = [];
    // Here goes the actual Observer management infrastructure. Note that it's
    // not everything that our class is responsible for. Its primary business
    // logic is listed below these methods.
    /**
     * @var array
     */
    private $observers = [];
    public function __construct()
    {
        // A 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(\SplObserver $observer, string $event = "*"): void
    {
        $this->initEventGroup($event);
        $this->observers[$event][] = $observer;
    }
    public function detach(\SplObserver $observer, string $event = "*"): void
    {
        foreach ($this->getEventObservers($event) as $key => $s) {
            if ($s === $observer) {
                unset($this->observers[$event][$key]);
            }
        }
    }
    public function notify(string $event = "*", $data = null): void
    {
        echo "UserRepository: Broadcasting the '$event' event.\n";
        foreach ($this->getEventObservers($event) as $observer) {
            $observer->update($this, $event, $data);
        }
    }
    // Here are the methods representing the business logic of the class.
    public function initialize($filename): void
    {
        echo "UserRepository: Loading user records from a file.\n";
        // ...
        $this->notify("users:init", $filename);
    }
    public function createUser(array $data): 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;
        $this->notify("users:created", $user);
        return $user;
    }
    public function updateUser(User $user, array $data): ?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);
        $this->notify("users:updated", $user);
        return $user;
    }
    public function deleteUser(User $user): void
    {
        echo "UserRepository: Deleting a user.\n";
        $id = $user->attributes["id"];
        if (!isset($this->users[$id])) {
            return;
        }
        unset($this->users[$id]);
        $this->notify("users:deleted", $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);
    }
}
/**
 * This Concrete Component logs any events it's subscribed to.
 */
class Logger implements \SplObserver
{
    private $filename;
    public function __construct($filename)
    {
        $this->filename = $filename;
        if (file_exists($this->filename)) {
            unlink($this->filename);
        }
    }
    public function update(\SplSubject $repository, string $event = null, $data = null): void
    {
        $entry = date("Y-m-d H:i:s") . ": '$event' with data '" . json_encode($data,320) . "'\n";
        file_put_contents($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 \SplObserver
{
    private $adminEmail;
    public function __construct($adminEmail)
    {
        $this->adminEmail = $adminEmail;
    }
    public function update(\SplSubject $repository, string $event = null, $data = null): void
    {
        // mail($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();
$repository->attach(new Logger(__DIR__ . "/log.txt"), "*");
$repository->attach(new OnboardingNotification("1@example.com"), "users:created");
$repository->initialize(__DIR__ . "/users.csv");
// ...
$user = $repository->createUser([
    "name" => "John Smith",
    "email" => "john99@example.com",
]);
// ...
$repository->deleteUser($user);