设计模式——观察者模式

说明

示例

下面看下观察者模式的代码实现

interface Observer{
    public function update();
}

class Observer1 implements Observer{
    public function update(){
        echo "observer1 has received!" . PHP_EOL;
    }
}

class Observer2 implements Observer{
    public function update(){
        echo "observer2 has received!" . PHP_EOL;
    }
}

interface Subject{
    public function add(Observer $observer);
    public function del(Observer $observer);
    public function notifyObservers();
    public function operation();
}

abstract class AbstractSubject implements Subject{
    private $vector = [];
    public function add(Observer $observer){
        $this->vector[] = $observer;
    }
    public function del(Observer $observer){
        $index = array_search($observer,$this->vector);
        unset($this->vector[$index]);
    }
    public function notifyObservers(){
        foreach ($this->vector as $value){
            $value->update();
        }
    }
}

class MySubject extends AbstractSubject{
    public function operation(){
        echo "update self!" . PHP_EOL;
        $this->notifyObservers();
    }
}


// 调用
$sub = new MySubject();
$sub->add(new Observer1());
$sub->add(new Observer2());
$sub->operation();
/**
 * output:
 * update self!
 * observer1 has received!
 * observer2 has received!
 */

总结