设计模式之观察者模式(php实现)

/** * 当对象间存在一对多关系时，则使用观察者模式（Observer Pattern）。 * 比如，当一个对象被修改时，则会自动通知它的依赖对象。观察者模式属于行为型模式。 * 一个对象（目标对象）的状态发生改变，所有的依赖对象（观察者对象）都将得到通知，进行广播通知。 */

<?phpnamespace Observer;class Subject{ ???private $state; ???private $observers = []; ???public function getState() ???{ ???????return $this->state; ???} ???public function seState($state) ???{ ???????$this->state = $state; ???????$this->notifyAllObjects(); ???} ???public function register(Observer $object) ???{ ???????$this->observers[] = $object; ???} ???public function remove($object) ???{ ???????foreach ($this->observers as $key => $observer) { ???????????if ($observer == $object){ ???????????????unset($this->observers[$key]); ???????????} ???????} ???} ???public function notifyAllObjects() ???{ ???????foreach ($this->observers as $observer) { ???????????$observer->update(); ???????} ???}}

<?phpnamespace Observer;abstract class Observer{ ???protected $subject; ???public abstract function update();}

<?phpnamespace Observer;class ObserverA extends Observer{ ???private $myState = ‘init A‘; ???public function __construct(Subject $subject) ???{ ???????$this->subject = $subject; ???????$this->subject->register($this); ???} ???public function update() ???{ ???????$this->myState = $this->subject->getState(); ???} ???public function getSate() ???{ ???????return "ObserverA get state:".$this->myState; ???}}

<?phpnamespace Observer;class ObserverB extends Observer{ ???private $myState = ‘init B‘; ???public function __construct(Subject $subject) ???{ ???????$this->subject = $subject; ???????$this->subject->register($this); ???} ???public function update() ???{ ???????$this->myState = $this->subject->getState(); ???} ???public function getSate() ???{ ???????return "ObserverB get state:".$this->myState; ???}}

<?phpspl_autoload_register(function ($className){ ???$className = str_replace(‘\\‘,‘/‘,$className); ???include $className.".class.php";});use Observer\ObserverA;use Observer\ObserverB;use Observer\Subject;/*

ObserverA get state:init A
ObserverB get state:init B
ObserverA get state:hello
ObserverB get state:hello
*/

$subject = new Subject(); $objectA = new ObserverA($subject); $objectB = new ObserverB($subject); echo $objectA->getSate(); echo ‘<br/>‘; echo $objectB->getSate(); echo ‘<br/>‘; $subject->seState("hello"); echo $objectA->getSate(); echo ‘<br/>‘; echo $objectB->getSate(); echo ‘<br/>‘;