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--- development:software-architecture:design-patterns:observer [2024/08/13 10:09] – tungnt
+++ development:software-architecture:design-patterns:observer [2024/08/19 09:51] (current) – [Ví dụ 3:] tungnt
@@ Line 10: / Line 10: @@
 {{ :development:software-architecture:design-patterns:observer-comic-1-en-2x.png |}}
+**Sử dụng 2 interface có sẵn của PHP (SplSubject, SplObserver):**
+  * http://php.net/manual/en/class.splsubject.php
+  * http://php.net/manual/en/class.splobserver.php
+  * https://www.php.net/manual/en/class.splobjectstorage.php
 ===== Ví dụ 1: =====
+<file php>
+<?php
+/**
+ * Subject,that who makes news
+ */
+class Newspaper implements \SplSubject{
+    private $name;
+    private $observers = array();
+    private $content;
+    public function __construct($name) {
+        $this->name = $name;
+    }
+    //add observer
+    public function attach(\SplObserver $observer) {
+        $this->observers[] = $observer;
+    }
+    //remove observer
+    public function detach(\SplObserver $observer) {
+        $key = array_search($observer,$this->observers, true);
+        if($key){
+            unset($this->observers[$key]);
+        }
+    }
+    //set breakouts news
+    public function breakOutNews($content) {
+        $this->content = $content;
+        $this->notify();
+    }
+    public function getContent() {
+        return $this->content." ({$this->name})";
+    }
+    //notify observers(or some of them)
+    public function notify() {
+        foreach ($this->observers as $value) {
+            $value->update($this);
+        }
+    }
+}
+/**
+ * Observer,that who recieves news
+ */
+class Reader implements SplObserver{
+    private $name;
+    public function __construct($name) {
+        $this->name = $name;
+    }
+    public function update(\SplSubject $subject) {
+        echo $this->name.' is reading breakout news <b>'.$subject->getContent().'</b><br>';
+    }
+}
+$newspaper = new Newspaper('Newyork Times');
+$allen = new Reader('Allen');
+$jim = new Reader('Jim');
+$linda = new Reader('Linda');
+//add reader
+$newspaper->attach($allen);
+$newspaper->attach($jim);
+$newspaper->attach($linda);
+//remove reader
+$newspaper->detach($linda);
+//set break outs
+$newspaper->breakOutNews('USA break down!');
+//=====output======
+//Allen is reading breakout news USA break down! (Newyork Times)
+//Jim is reading breakout news USA break down! (Newyork Times)
+</file>
+===== Ví dụ 2: =====
+<file php>
+<?php
+// Example implementation of Observer design pattern:
+class MyObserver1 implements SplObserver {
+    public function update(SplSubject $subject) {
+        echo __CLASS__ . ' - ' . $subject->getName();
+    }
+}
+class MyObserver2 implements SplObserver {
+    public function update(SplSubject $subject) {
+        echo __CLASS__ . ' - ' . $subject->getName();
+    }
+}
+class MySubject implements SplSubject {
+    private $_observers;
+    private $_name;
+    public function __construct($name) {
+        $this->_observers = new SplObjectStorage();
+        $this->_name = $name;
+    }
+    public function attach(SplObserver $observer) {
+        $this->_observers->attach($observer);
+    }
+    public function detach(SplObserver $observer) {
+        $this->_observers->detach($observer);
+    }
+    public function notify() {
+        foreach ($this->_observers as $observer) {
+            $observer->update($this);
+        }
+    }
+    public function getName() {
+        return $this->_name;
+    }
+}
+$observer1 = new MyObserver1();
+$observer2 = new MyObserver2();
+$subject = new MySubject("test");
+$subject->attach($observer1);
+$subject->attach($observer2);
+$subject->notify();
+/*
+will output:
+MyObserver1 - test
+MyObserver2 - test
+*/
+$subject->detach($observer2);
+$subject->notify();
+/*
+will output:
+MyObserver1 - test
+*/
+?>
+</file>
+===== Ví dụ 3: =====
+{{ :development:software-architecture:design-patterns:observerstructure-2x.png |}}
+<file php>
+<?php
+namespace RefactoringGuru\Observer\Conceptual;
+/**
+ * PHP has a couple of built-in interfaces related to the Observer pattern.
+ *
+ * Here's what the Subject interface looks like:
+ *
+ * @link http://php.net/manual/en/class.splsubject.php
+ *
+ *     interface SplSubject
+ *     {
+ *         // Attach an observer to the subject.
+ *         public function attach(SplObserver $observer);
+ *
+ *         // Detach an observer from the subject.
+ *         public function detach(SplObserver $observer);
+ *
+ *         // Notify all observers about an event.
+ *         public function notify();
+ *     }
+ *
+ * There's also a built-in interface for Observers:
+ *
+ * @link http://php.net/manual/en/class.splobserver.php
+ *
+ *     interface SplObserver
+ *     {
+ *         public function update(SplSubject $subject);
+ *     }
+ */
+/**
+ * The Subject owns some important state and notifies observers when the state
+ * changes.
+ */
+class Subject implements \SplSubject
+{
+    /**
+     * @var int For the sake of simplicity, the Subject's state, essential to
+     * all subscribers, is stored in this variable.
+     */
+    public $state;
+    /**
+     * @var \SplObjectStorage List of subscribers. In real life, the list of
+     * subscribers can be stored more comprehensively (categorized by event
+     * type, etc.).
+     */
+    private $observers;
+    public function __construct()
+    {
+        $this->observers = new \SplObjectStorage();
+    }
+    /**
+     * The subscription management methods.
+     */
+    public function attach(\SplObserver $observer): void
+    {
+        echo "Subject: Attached an observer.\n";
+        $this->observers->attach($observer);
+    }
+    public function detach(\SplObserver $observer): void
+    {
+        $this->observers->detach($observer);
+        echo "Subject: Detached an observer.\n";
+    }
+    /**
+     * Trigger an update in each subscriber.
+     */
+    public function notify(): void
+    {
+        echo "Subject: Notifying observers...\n";
+        foreach ($this->observers as $observer) {
+            $observer->update($this);
+        }
+    }
+    /**
+     * Usually, the subscription logic is only a fraction of what a Subject can
+     * really do. Subjects commonly hold some important business logic, that
+     * triggers a notification method whenever something important is about to
+     * happen (or after it).
+     */
+    public function someBusinessLogic(): void
+    {
+        echo "\nSubject: I'm doing something important.\n";
+        $this->state = rand(0, 10);
+        echo "Subject: My state has just changed to: {$this->state}\n";
+        $this->notify();
+    }
+}
+/**
+ * Concrete Observers react to the updates issued by the Subject they had been
+ * attached to.
+ */
+class ConcreteObserverA implements \SplObserver
+{
+    public function update(\SplSubject $subject): void
+    {
+        if ($subject->state < 3) {
+            echo "ConcreteObserverA: Reacted to the event.\n";
+        }
+    }
+}
+class ConcreteObserverB implements \SplObserver
+{
+    public function update(\SplSubject $subject): void
+    {
+        if ($subject->state == 0 || $subject->state >= 2) {
+            echo "ConcreteObserverB: Reacted to the event.\n";
+        }
+    }
+}
+/**
+ * The client code.
+ */
+$subject = new Subject();
+$o1 = new ConcreteObserverA();
+$subject->attach($o1);
+$o2 = new ConcreteObserverB();
+$subject->attach($o2);
+$subject->someBusinessLogic();
+$subject->someBusinessLogic();
+$subject->detach($o2);
+$subject->someBusinessLogic();
+</file>
+===== Ví dụ 4: =====
 <file php>
@@ Line 224: / Line 538: @@
 </file>
-====== Tham khảo ======
+===== Tham khảo =====
   * https://refactoring.guru/design-patterns/observer
   * https://moezmissaoui.medium.com/the-observer-design-pattern-in-laravel-a-comprehensive-guide-cdac37601e7a
   * https://medium.com/@mansha99/better-laravel-monoliths-observer-pattern-ff9119db5b65
+  * https://www.youtube.com/watch?v=7J5pRc2vzWk