An article to talk about DI dependency injection in php

What is DI dependency injection? The following article will give you an in-depth understanding of DI dependency injection in php. I hope it will be helpful to you!

What is DI/Dependency Injection

• Dependency Injection DIIn fact, it essentially means Dependence on the class is completed through the constructorAutomatic injection
• In layman's terms, it means that you are currently operating a class, but some methods or functions of this class cannot be achieved by relying on this class alone. It can be completed only with the help of another class
The most direct sign is when the parameter data is passed as an object. Strictly speaking, you
• want to operate one class in another class. There is an interdependence relationship between the two classes. The method of passing parameters is calledinjection

The reason why dependency injection appears

When dependency injection is not used,
• phpWhen you need to use another class in one class , often the following operations are performed
For example, if I need to use the
• adapterclass in thecontainerclass, I need to instantiate it before use
If a large number of external classes need to be used, this will cause
• the degree of coupling to be too high, which can easily lead to latermaintenance difficulties
In lay terms, That is,
• containercannot work without external classes. This is calledtoo high coupling

adapter = new adapter(); } }

Simple dependency injection

The coupling degree of the above code is too high, which leads to the emergence of
• Dependency Injection, mainly fordecoupling
For the following cases, we only You need to pass in the class object that needs to be operated
• Dependency injectionThe parameters of the operation areobjects, not ordinary parameters. Do you have a better understanding?
But such a simple dependency injection will cause if you depend on a lot of classes, it will take a long time when you pass parameters, which will easily
• confuse

adapter = $adapter; } }

High-level dependency injection

In order to solve the above problem of
• parameter confusion, at this time, dependency injection has been optimizedThrough the magic method,
  __getSet the object
At this time, we can solve the problem of too many dependencies and confusing parameters

instance[$name] = $value; } } $container = new container(); $container->adapter = new adapter(); $container->autofelix = new autofelix();

Dependency injection application

We first define a
• container class, which is mainly used toinjectthe class you want to operate
into the container. At this time, you only need to pass the
• objectof the container

instance[$name] = $value; } } class adapter { public $name = '我是调度器'; } $container = new container(); $container->adapter = new adapter(); class autofelix { private $container; public function __construct(container $container) { $this->container = $container; } public function who($class) { return $this->container->instance[$class]->name; } } $autofelix = new autofelix($container); $who = $autofelix->who('adapter'); var_dump($who); //我是调度器

Dependency Injection Advanced Optimization

above In the application, we
• directlyinject the instantiated objects into the container
This will cause all objects to be instantiated before they are used, causing
• resource loss Loss
We can
• pass in the closure, so that the object will not be instantiated and injected. When you need to use it yourself, instantiate it again, which can reduceLoss of server resources

adapter = new adapter(); //高阶优化 $container = new container(); $container->adapter = function () { return new adapter(); };

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