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
- 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,
- php
When you need to use another class in one class , often the following operations are performedFor example, if I need to use the - adapter
class 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, - container
cannot work without external classes. This is calledtoo 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 fordecoupling 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 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
<?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 optimizedThrough the magic method,
__getSet the objectAt 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 toinjectthe 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 containerThis 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 reduceLoss of server resources
<?php
$container = new container();
$container->adapter = new adapter();
//高阶优化
$container = new container();
$container->adapter = function () {
return new adapter();
};PHP Video Tutorial"
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