Behavioral定义对象间一种一对多的依赖关系，使得当一个对象改变状态，则所有依赖于它的对象都会得到通知并被自动更新。
Subject 被观察者。是一个接口或者是抽象类，定义被观察者必须实现的职责，它必须能偶动态地增加、取消观察者，管理观察者并通知观察者。
Observer 观察者。观察者接收到消息后，即进行 update 更新操作，对接收到的信息进行处理。
ConcreteSubject 具体的被观察者。定义被观察者自己的业务逻辑，同时定义对哪些事件进行通知。
ConcreteObserver 具体观察者。每个观察者在接收到信息后处理的方式不同，各个观察者有自己的处理逻辑。
观察者模式简单的理解，就是当一个类改变的时候，通知另外一个类进行做出处理。比如我们用户在注册成功的时候，会发送短信提醒。我们可以利用观察者模式，实现应用的解耦。
//抽象主题类
interface Subject
{
public function attach(Observer $Observer);
public function detach(Observer $observer);
//通知所有注册过的观察者对象
public function notifyObservers();
}
//具体主题角色
class ConcreteSubject implements Subject
{
private $_observers;
public function __construct()
{
$this->_observers = array();
}
//增加一个观察者对象
public function attach(Observer $observer)
{
return array_push($this->_observers,$observer);
}
//删除一个已经注册过的观察者对象
public function detach(Observer $observer)
{
$index = array_search($observer,$this->_observers);
if($index === false || !array_key_exists($index, $this->_observers))
return false;
unset($this->_observers[$index]);
return true;
}
//通知所有注册过的观察者
public function notifyObservers()
{
if(!is_array($this->_observers)) return false;
foreach($this->_observers as $observer)
{
$observer->update();
}
return true;
}
}
//抽象观察者角色
interface Observer
{
//更新方法
public function update();
}
//观察者实现
class ConcreteObserver implements Observer
{
private $_name;
public function __construct($name)
{
$this->_name = $name;
}
//更新方法
public function update()
{
echo 'Observer'.$this->_name.' has notify';
}
}
$Subject = new ConcreteSubject();
//添加第一个观察者
$observer1 = new ConcreteObserver('baixiaoshi');
$Subject->attach($observer1);
echo 'the first notify:';
$Subject->notifyObservers();
//添加第二个观察者
$observer2 = new ConcreteObserver('hurong');
echo '<br/>second notify:';
$Subject->attach($observer2);
- 利用SPLObserver 和SplSubject
SplSubject {
/* 方法 */
abstract public void attach ( SplObserver $observer )
abstract public void detach ( SplObserver $observer )
abstract public void notify ( void )
}
SplObserver {
/* 方法 */
abstract public void update ( SplSubject $subject )
}/**
* 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!');