start a restructure

Behavioral/Observer/README.md

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+# Observer
+
+## Purpose
+
+To implement a publish/subscribe behaviour to an object, whenever a "Subject" object changes it's state, the attached
+"Observers" will be notified. It is used to shorten the amount of coupled objects and uses loose coupling instead.
+
+## Examples
+
+* a message queue system is observed to show the progress of a job in a GUI
+
+## Note
+
+PHP already defines two interfaces that can help to implement this pattern: SplObserver and SplSubject.

Behavioral/Observer/Test/ObserverTest.php

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+<?php
+
+namespace DesignPatterns\Tests\Observer;
+
+use DesignPatterns\Observer\UserObserver;
+use DesignPatterns\Observer\User;
+
+/**
+ * ObserverTest tests the Observer pattern
+ */
+class ObserverTest extends \PHPUnit_Framework_TestCase
+{
+
+    protected $observer;
+
+    protected function setUp()
+    {
+        $this->observer = new UserObserver();
+    }
+
+    /**
+     * Tests the notification
+     */
+    public function testNotify()
+    {
+        $this->expectOutputString('DesignPatterns\Observer\User has been updated');
+        $subject = new User();
+
+        $subject->attach($this->observer);
+        $subject->property = 123;
+    }
+
+    /**
+     * Tests the subscribing
+     */
+    public function testAttachDetach()
+    {
+        $subject = new User();
+        $this->assertAttributeEmpty('observers', $subject);
+        $subject->attach($this->observer);
+        $this->assertAttributeNotEmpty('observers', $subject);
+        $subject->detach($this->observer);
+        $this->assertAttributeEmpty('observers', $subject);
+    }
+
+    /**
+     * Tests the update() invocation on a mockup
+     */
+    public function testUpdateCalling()
+    {
+        $subject = new User();
+        $observer = $this->getMock('SplObserver');
+        $subject->attach($observer);
+
+        $observer->expects($this->once())
+                ->method('update')
+                ->with($subject);
+
+        $subject->notify();
+    }
+
+}

Behavioral/Observer/User.php

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+<?php
+
+namespace DesignPatterns\Observer;
+
+/**
+ * Observer pattern : The observed object (the subject)
+ * 
+ * The subject maintains a list of Observers and sends notifications.
+ *
+ */
+class User implements \SplSubject
+{
+    /**
+     * user data
+     *
+     * @var array
+     */
+    protected $data = array();
+
+    /**
+     * observers
+     *
+     * @var array
+     */
+    protected $observers = array();
+
+    /**
+     * attach a new observer
+     *
+     * @param \SplObserver $observer
+     *
+     * @return void
+     */
+    public function attach(\SplObserver $observer)
+    {
+        $this->observers[] = $observer;
+    }
+
+    /**
+     * detach an observer
+     *
+     * @param \SplObserver $observer
+     *
+     * @return void
+     */
+    public function detach(\SplObserver $observer)
+    {
+        $index = array_search($observer, $this->observers);
+
+        if (false !== $index) {
+            unset($this->observers[$index]);
+        }
+    }
+
+    /**
+     * notify observers
+     *
+     * @return void
+     */
+    public function notify()
+    {
+        /** @var SplObserver $observer */
+        foreach ($this->observers as $observer) {
+            $observer->update($this);
+        }
+    }
+
+    /**
+     * Ideally one would better write setter/getter for all valid attributes and only call notify()
+     * on attributes that matter when changed
+     *
+     * @param string $name
+     * @param mixed  $value
+     *
+     * @return void
+     */
+    public function __set($name, $value)
+    {
+        $this->data[$name] = $value;
+
+        // notify the observers, that user has been updated
+        $this->notify();
+    }
+}

Behavioral/Observer/UserObserver.php

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+<?php
+
+namespace DesignPatterns\Observer;
+
+/**
+ * class UserObserver
+ */
+class UserObserver implements \SplObserver
+{
+    /**
+     * This is the only method to implement as an observer.
+     * It is called by the Subject (usually by SplSubject::notify() )
+     * 
+     * @param \SplSubject $subject
+     */
+    public function update(\SplSubject $subject)
+    {
+        echo get_class($subject) . ' has been updated';
+    }
+}