大话设计模式第十四章--观察者模式

<?php
abstract class Subject {
    private $_observers = array();

    public function attach(Observer $observer) {
        $this->_observers[] = $observer;
    }

    public function detach(Observer $observer) {
        if (isset($this->_observers[$observer])) {
            unset($this->_observers[$observer]);
        }
    }

    public function notify() {
        foreach ($this->_observers as $observer) {
            $observer->update();
        }
    }
}

abstract class Observer {
    abstract public function update();
}

class Concrete_subject extends Subject {
    private $subject_state;

    public function __set($param, $value) {
        if ($param == ‘subject_state‘) {
            $this->subject_state = $value;
        }
    }
    public function __get($param) {
        if ($param == ‘subject_state‘) {
            return $this->subject_state;
        }
    }
}

class Concrete_observer extends Observer {
    private $name;
    private $observer_state;
    private $subject;

    public function __construct(Concrete_subject $subject, string $name) {
        $this->subject = $subject;
        $this->name = $name;
    }

    public function update() {
        $this->observer_state = $this->subject->subject_state;
        echo "OBSERVER ".$this->name." ‘s STATUS IS".$this->observer_state."<br/>";
    }

    public function __set($param, $value) {
        if ($param == ‘subject‘) {
            $this->subject = $value;
        }
    }
    public function __get($param) {
        if ($param == ‘subject‘) {
            return $this->subject;
        }
    }
}

//CLIENT CODE
$s = new Concrete_subject();
$s->attach(new Concrete_observer($s, ‘X‘));
$s->attach(new Concrete_observer($s, ‘Y‘));
$s->attach(new Concrete_observer($s, ‘Z‘));

$s->subject_state = ‘ABC‘;
$s->notify();