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 DI
In 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
- want to operate one class in another class
. There is an interdependence relationship between the two classes. The method of passing parameters is called
injection
The reason why dependency injection appears
- When dependency injection is not used,
- php
When you need to use another class in one class , often the following operations are performed
For example, if I need to use the - adapter
class in the
containerclass, 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 later
maintenance difficulties In lay terms, That is, - container
cannot work without external classes. This is called
too high coupling
<?php class container { private $adapter; public function __construct() { $this->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 for
decoupling For the following cases, we only You need to pass in the class object that needs to be operated - Dependency injection
The parameters of the operation are
objects, 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
<?php class container { private $adapter; public function __construct(adapter $adapter) { $this->adapter = $adapter; } }
High-level dependency injection
- In order to solve the above problem of
- parameter confusion
, at this time, dependency injection has been optimized
Through the magic method,
__getSet the object
At this time, we can solve the problem of too many dependencies and confusing parameters
<?php class container { public $instance = []; public function __set($name, $value) { $this->instance[$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 to
injectthe class you want to operate
into the container. At this time, you only need to pass the - object
of the container
<?php class container { public $instance = []; public function __set($name, $value) { $this->instance[$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
- directly
inject the instantiated objects into the container
This will cause all objects to be instantiated before they are used, causing - resource loss Loss
- 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 reduce
Loss of server resources
<?php $container = new container(); $container->adapter = new adapter(); //高阶优化 $container = new container(); $container->adapter = function () { return new adapter(); };
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