The SplSubject interface

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

简介

The SplSubject interface is used alongside SplObserver to implement the Observer Design Pattern.

接口摘要

interface SplSubject {

/* 方法 */

public attach(SplObserver $observer): void

public detach(SplObserver $observer): void

public notify(): void

}


<?php 

// Example implementation of Observer design pattern:

class MyObserver1 implements SplObserver {
    public function update(SplSubject $subject) {
        echo __CLASS__ . ' - ' . $subject->getName();
    }
}

class MyObserver2 implements SplObserver {
    public function update(SplSubject $subject) {
        echo __CLASS__ . ' - ' . $subject->getName();
    }
}

class MySubject implements SplSubject {
    private $_observers;
    private $_name;

    public function __construct($name) {
        $this->_observers = new SplObjectStorage();
        $this->_name = $name;
    }

    public function attach(SplObserver $observer) {
        $this->_observers->attach($observer);
    }

    public function detach(SplObserver $observer) {
        $this->_observers->detach($observer);
    }

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

    public function getName() {
        return $this->_name;
    }
}

$observer1 = new MyObserver1();
$observer2 = new MyObserver2();

$subject = new MySubject("test");

$subject->attach($observer1);
$subject->attach($observer2);
$subject->notify();

/* 
will output:

MyObserver1 - test
MyObserver2 - test
*/

$subject->detach($observer2);
$subject->notify();

/* 
will output:

MyObserver1 - test
*/

?>

down

xedin dot unknown at gmail dot com ¶

3 years ago


For a few years, I've made a few attempts to understand the architecture behind the Subject/Observer pair. Recently I tried again. I just could not imagine why someone would design this in the way it is documented.  I mean, "what were they thinking?!", I thought. The if things outside of the Subject could tell it when to notify observers, that would completely break encapsulation. Because only the subject can know when events occur inside of it. And therefore, exposing `notify()` would be a huge violation to many principles of good OOP design.

However, I have come up with one scenario where this would be valid. That is, if the Subject represents a Hook, like in WordPress. For example, in an event system where events are invoked with a name or code, a Hook could represent a named event in the system, and by calling `notify()` from outside the dispatcher could notify observers. If this is the intended scenario, then the problems are mostly with naming: the name "Subject" implies that it is what is being observed, and the Observer pattern is different.

down

Anonymous ¶

9 years ago


<?php
class Observable implements SplSubject
{
    private $storage;

    function __construct()
    {
        $this->storage = new SplObjectStorage();
    }

    function attach(SplObserver $observer)
    {
        $this->storage->attach($observer);
    }

    function detach(SplObserver $observer)
    {
        $this->storage->detach($observer);
    }

    function notify()
    {
        foreach ($this->storage as $obj) {
            $obj->update($this);
        }
    }
    //...
}

abstract class Observer implements SplObserver
{
    private $observable;

    function __construct(Observable $observable)
    {
        $this->observable = $observable;
        $observable->attach($this);
    }

    function update(SplSubject $subject)
    {
        if ($subject === $this->observable) {
            $this->doUpdate($subject);
        }
    }

    abstract function doUpdate(Observable $observable);
}

class ConcreteObserver extends Observer
{
    function doUpdate(Observable $observable)
    {
        //...
    }
}

$observable = new Observable();
new ConcreteObserver($observable);

down

aiddroid at example dot com ¶

8 years ago


/**
 * 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 $this->content." (by {$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>';
    }
}

//classes test
$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!');

//=========output==========
//Allen is reading breakout news USA break down! (by Newyork Times)
//Jim is reading breakout news USA break down! (by Newyork Times)

add a note

官方地址：https://www.php.net/manual/en/class.splsubject.php

有任何技术问题请点击这里网站运营推广招聘

IT PHP 编程语言 Linux 开发编程科技 Elasticsearch HTML/CSS/XML 网络 JAVA NoSQL 数据库面试 C/C++ Golang Git 算法操作系统正则表达式 Redis 互联网 MySql JavaScript 运维软件国际架构设计 Mac OS TCP/IP Excel Vim Windows Socket Oracle VR MongoDB Python 运营 MemCache 商业硬件电子娱乐设计 nginx 摄影游戏 WordPress HTTP 团建数码电器

php7 安装fileinfo扩展 preg_split — 通过一个正则表达式分隔字符串 php位值,解决 PHP 中 usort 在值相同时改变原始位置的问题 [PHP] inet_pton/inet_ntop IP地址转换函数 array_multisort() 多字段排序 PHPMailer设置utf8 PHPMailer字符集CharSet ADORecordSet对象 adodb手册 PHP 8.1 [鸟哥]PHP_INT_MIN 和 -9223372036854775808 opcache预加载 Composer的Packagist资源 mysql面试题 [鸟哥]PHP FFI详解 - 一种全新的PHP扩展方式 PHP7添加redis扩展 Packagist / Composer 中国全量镜像 PHP获取指定函数定义在哪个文件中及行号 PHP mkdir()写出来的权限与mode值不符合 adodb连接mysql多个数据库的问题 PHPstorm 里面Terminal 不能使用 esc键吗退出编辑模式吗

略微加速

PHP官方手册 - 互联网笔记

The SplSubject interface

简介

接口摘要

目录

User Contributed Notes 4 notes