Detailed explanation of php observer pattern
This article mainly introduces the detailed explanation of the PHP observer mode. Interested friends can refer to it. I hope it will be helpful to everyone.
1. Intention
Define a one-to-many dependency relationship between objects. When the state of an object changes, all objects that depend on it All objects are notified and automatically updated [GOF95]
Also known as publish-subscribe (Publish-Subscribe) mode, model-view (Model-View) mode, source-listener (Source-Listener) mode, or slave Dependents pattern
2. Observer pattern structure diagram
#3. The main role in the observer patternAbstract subject (Subject) role:The subject role saves all references to the observer object in a collection, each subject There can be any number of observers. The abstract theme provides an interface for adding and removing observer objects.
Abstract Observer (Observer) role: Define an interface for all specific observers and update themselves when the subject of observation changes.
Concrete subject (ConcreteSubject) role: Store the relevant state to the specific observer object. When the internal state of the specific subject changes, notify all registered observers. Concrete theme roles are usually implemented using a concrete subclass.
Concrete Observer (ConcretedObserver) role: Store a specific subject object, store related states, and implement the update interface required by the abstract observer role to make its own state consistent with the state of the subject.
4. Advantages and disadvantages of the observer pattern
Advantages of the observer pattern:1. The degree of coupling between the observer and the subject Smaller; 2. Supports broadcast communication;
Disadvantages of the observer mode:
1. Since the observer does not know the existence of other observers, it may have a negative impact on the final cost of changing the target. Nothing is known. This may cause unexpected updates.
5. Applicable scenarios of the observer pattern1. When an abstract model has two aspects, one of which depends on the other. 2. When changing one object requires changing other objects at the same time, it is not known how many objects need to be changed. 3. When an object must notify other objects, it cannot assume who the other objects are. In other words, you don't want these objects to be tightly coupled.
6. Observer pattern and other patternsMediator pattern (Mediator):By encapsulating complex update semantics, ChangeManager acts as a target and an observer. intermediary between. Singleton mode (singleton mode):
ChangeManager can use the Singleton mode to ensure that it is unique and globally accessible.
7. Observer Mode PHP Example<?php
/**
* 抽象主题角色
*/
interface Subject {
/**
* 增加一个新的观察者对象
* @param Observer $observer
*/
public function attach(Observer $observer);
/**
* 删除一个已注册过的观察者对象
* @param Observer $observer
*/
public function detach(Observer $observer);
/**
* 通知所有注册过的观察者对象
*/
public function notifyObservers();
}
/**
* 具体主题角色
*/
class ConcreteSubject implements Subject {
private $_observers;
public function __construct() {
$this->_observers = array();
}
/**
* 增加一个新的观察者对象
* @param Observer $observer
*/
public function attach(Observer $observer) {
return array_push($this->_observers, $observer);
}
/**
* 删除一个已注册过的观察者对象
* @param Observer $observer
*/
public function detach(Observer $observer) {
$index = array_search($observer, $this->_observers);
if ($index === FALSE || ! array_key_exists($index, $this->_observers)) {
return FALSE;
}
unset($this->_observers[$index]);
return TRUE;
}
/**
* 通知所有注册过的观察者对象
*/
public function notifyObservers() {
if (!is_array($this->_observers)) {
return FALSE;
}
foreach ($this->_observers as $observer) {
$observer->update();
}
return TRUE;
}
}
/**
* 抽象观察者角色
*/
interface Observer {
/**
* 更新方法
*/
public function update();
}
class ConcreteObserver implements Observer {
/**
* 观察者的名称
* @var <type>
*/
private $_name;
public function __construct($name) {
$this->_name = $name;
}
/**
* 更新方法
*/
public function update() {
echo 'Observer', $this->_name, ' has notified.<br />';
}
}
/**
* 客户端
*/
class Client {
/**
* Main program.
*/
public static function main() {
$subject = new ConcreteSubject();
/* 添加第一个观察者 */
$observer1 = new ConcreteObserver('Martin');
$subject->attach($observer1);
echo '<br /> The First notify:<br />';
$subject->notifyObservers();
/* 添加第二个观察者 */
$observer2 = new ConcreteObserver('phppan');
$subject->attach($observer2);
echo '<br /> The Second notify:<br />';
$subject->notifyObservers();
/* 删除第一个观察者 */
$subject->detach($observer1);
echo '<br /> The Third notify:<br />';
$subject->notifyObservers();
}
}
Client::main();
?>
Related recommendations:
PHP method to implement asterisk to hide username, mobile phone and email addressphp WeChat public platform configuration interface development Detailed explanation of the method examples of the programDetailed explanation of the method of PHP implementation of the previous article and the next articleThe above is the detailed content of Detailed explanation of php observer pattern. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian
Dec 24, 2024 pm 04:42 PM
PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati
7 PHP Functions I Regret I Didn't Know Before
Nov 13, 2024 am 09:42 AM
If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op
How To Set Up Visual Studio Code (VS Code) for PHP Development
Dec 20, 2024 am 11:31 AM
Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c
Explain JSON Web Tokens (JWT) and their use case in PHP APIs.
Apr 05, 2025 am 12:04 AM
JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,
PHP Program to Count Vowels in a String
Feb 07, 2025 pm 12:12 PM
A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total
How do you parse and process HTML/XML in PHP?
Feb 07, 2025 am 11:57 AM
This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an
Explain late static binding in PHP (static::).
Apr 03, 2025 am 12:04 AM
Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.
What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases?
Apr 03, 2025 am 12:03 AM
What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
