Detailed explanation of PHP design pattern Observer pattern
Abstract: Yii2 events adopt the "observer mode". It is easier to understand the observer first and then learn the events.
What is it
First of all, don’t be intimidated by the name, look down, it’s really simple.
Let’s start with a more advanced definition: the observer pattern defines a one-to-many relationship between a series of objects. When an object changes state, other dependents will receive notifications.
Do you understand?
If you don’t understand, let’s give you a more realistic idea: the observer model is the model of ordering newspapers. You and some people order newspapers from a certain newspaper. As long as a new newspaper is published, the newspaper will deliver it to you. What you think specifically has nothing to do with the newspaper. As long as the newspaper doesn't close down, it will continue to send it to you.
Of course, you can also unsubscribe.
Observer Mode== Newspaper + People who subscribe to newspapers
No matter which definition you understand, remember one thing, "Observer Mode" is the most awesome The place is to loosely couple some classes that depend on each other. What does a great system look like? That is, the degree of dependence between each object is reduced to a freezing point, but interaction is still possible.
Code it
I think at this moment, you have already understood the observer pattern, but as a language article, it is impossible not to write some code. Let's use code to realize the above requirements.
Let’s start with a code that doesn’t use the observer pattern
class Video { public function new(){
$checkNewVideo = Video::find()->where("xxxxx")->one(); if($checkNewVideo){ // 通知各位
LaoWang::newVideo();
XiaoLi::newVideo();
ChuanPu::newVideo();
....... // 还有很多很多，比如在给某个集体客户群发、短信发等等等等
}
}
}// 具体实现$model = new Video();
$model->new();In fact, when the system is small, this is a very fast and effective way.
However, when the system becomes larger, this method immediately faces the problem of being difficult to expand and prone to errors.
For example, if Lao Wang no longer wants to subscribe, we need to change the source code.
For example, if another customer is added, we need to change the source code.
For example xxx, we all need to change the source code.
The coupling between these two objects is too high.
Solve it - use the observer pattern
Let’s improve the above code first
/**
* 被观察者接口
* 定义了一些公用方法声明，使用观察者模式的类都可以继承此接口
*/interface Observable { // 添加/注册观察者
public function attach(Observer $observer); // 删除观察者
public function detach(Observer $observer); // 触发通知
public function notify();
}class Video implements Observable { public $observers = [];// 订阅者
// 添加观察者
public function attach(Observer $observer){
$key = array_search($observer, $this->observers); if ($key === false) { $this->observers[] = $observer;
}
} // 删除观察者
public function detach(Observer $observer){
$key = array_search($observer, $this->observers); if ($key !== false) { unset($this->observers[$key]);
}
} // 通知所有观察者
public function notify(){ foreach ($this->observers as $observer) { // 把本类对象传给观察者
$observer->update($this);
}
} public function new(){
$checkNewVideo = Video::find()->where("xxxxx")->one(); if($checkNewVideo){ $this->notify();
}
}
}As you can see, the modified code does not care about who is sent to, it just It traverses the list of all observers and then tells them. The increase or decrease of observers will not have any impact on this type.
对于观察者，数字不定，随时有增减，因此我们定义了一个观察者接口开始抽象它们。
/**
* 观察者接口
*/interface Observer{ // 接收到通知的处理方法
public function update(Observable $observable);
}老王、小明、川普、冰冰订阅了视频
class LaoWang implements Observer { public function update(Observable $observable){ echo "立刻开始看视频";
}
}class XiaoMing implements Observer { public function update(Observable $observable){ echo "收到后忽略通知";
}
}class ChuanPu implements Observer { public function update(Observable $observable){ echo "收藏了一下，然后去wc看";
}
}class BingBing implements Observer { public function update(Observable $observable){ echo "立刻开始看视频";
}
}具体实现
$model = new Video(); $model->attach(new LaoWang()); $model->attach(new XiaoLi()); $model->attach(new ChuanPu()); $model->attach(new BingBing()); $model->new();
这样当我们再增加一个人加入 习大大 的时候，我们只需要增加一个习大大的观察者类，在实现的时候添加注册，而不需要去改Video类和其他的观察者类，将类之间的耦合降低了很多。
回头看
上面就是观察者模式，我们先预想一下我们的事件，假设我们定义了很多观察者代码，他们监听事件的发生，当一个事件被触发，这些观察者都会知道，执行各自的逻辑。
事件就是观察者模式的一种应用。
监听系统的某一个行为，实时获取并执行自己负责的代码。
The above is the detailed content of Detailed explanation of PHP design pattern 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.
