PHP深入觀察者模式

####觀察者模式* 設計觀察者是為了讓一個對象跟蹤某個狀態,知道狀態如何改變,一旦狀態改變,所有訂閱的對象都能得到通知#####使用SPL實現觀察者模式* Splsubject 介面有三個抽象方法 attach(),detach(),notify()這些方法不返回任何結果* SplObserver 介面有一個方法update()它會得到subject狀態的最新狀態並交給觀察者執行個體* SplObjectStorage 類描述為從對象到資料或對象集的一個映射```observers = new SplObjectStorage();    }    //添加觀察者    public function attach(\SplObserver $observer){        $this->observers->attach($observer);    }//刪除觀察者    public function detach(\SplObserver $observer){        $this->observers->detach($observer);    }    //通知轉寄    public function notify(){        foreach($this->observers as $observer){            $observer->update($this);        }    }    //設定資料    public function setData($dataNow){        $this->data = $dataNow;    }    public function getData(){        return $this->data;    }}//SPL具體觀察者class ConcreteObserver implements SplObserver{    public function update(SplSubject $subject)    {      echo $subject->getData();    }}class Client{    public function __construct()    {        echo "
 create three new concrete observers ";        //建立觀察者        $ob1 = new ConcreteObserver();        $ob2 = new ConcreteObserver();        $ob3 = new ConcreteObserver();        $subject = new ConcreteSubject();        $subject->setObservers();        $subject->setData("here is u data"."
");        $subject->attach($ob1);        $subject->attach($ob2);        $subject->attach($ob3);        $subject->notify();        echo "
 Reset data and reattach ob3
";        $subject->setData("more data that only"."
");        $subject->attach($ob3);        $subject->attach($ob2);        $subject->notify();    }}$data = new Client();```#####自由的PHP和觀察者模式```observers,$obser);    }    public function detachObser(Observer $obser){        //從數組中移除 資料        $position = 0;        foreach($this->observers as $viwer){            ++$position;            if($viwer == $obser){                array_splice($this->observers,($position),1);            }        }    }    public function notify(){        foreach($this->observers as $viewer){            //調用update方法            $viewer->update($this);        }    }}class ConcreteSubject extends Subject{    public function setState($stateSet){        $this->stateNow = $stateSet;    }    public function getState(){        return $this->stateNow;    }}class ConcreteObserverDT implements Observer{    private $currentState;    public function update(Subject $subject)    {       $this->currentState = $subject->getState();        echo "DT";    }}class ConcreObserverTablet implements Observer{    private $currentState;    public function update(Subject $subject)    {        $this->currentState = $subject->getState();        echo "tablet";    }}class ConcreObserverPhone implements Observer{    private $currentState;    public function update(Subject $subject)    {        $this->currentState = $subject->getState();        echo "phone";    }}class Client{    public function __construct()    {        $sub = new ConcreteSubject();        $ob1 = new ConcreObserverPhone();        $ob2 = new ConcreObserverTablet();        $ob3 = new ConcreteObserverDT();        $sub->attachObser($ob1);        $sub->attachObser($ob2);        $sub->attachObser($ob3);        $sub->setState("fuck");        $sub->detachObser($ob1);        $sub->notify();    }}$data = new Client();```

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