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Laravel实现构造函数自动依赖注入的方法

发布时间:2020-12-14 19:52:31 所属栏目:大数据 来源:网络整理
导读:《:Laravel实现构造函数自动依赖注入的方法》要点: 本文介绍了:Laravel实现构造函数自动依赖注入的方法,希望对您有用。如果有疑问,可以联系我们。 本篇章节讲解Laravel实现构造函数自动依赖注入的办法.供大家参考研究,具体如下: PHP编程 在Lar

《:Laravel实现构造函数自动依赖注入的方法》要点:
本文介绍了:Laravel实现构造函数自动依赖注入的方法,希望对您有用。如果有疑问,可以联系我们。

本篇章节讲解Laravel实现构造函数自动依赖注入的办法.分享给大家供大家参考,具体如下:PHP编程

在Laravel的构造函数中可以实现自动依赖注入,而不需要实例化之前先实例化需要的类,如代码所示:PHP编程

<?php
namespace LioHttpControllersForum;
use LioForumRepliesReplyRepository;
use LioForumThreadsThreadCreator;
use LioForumThreadsThreadCreatorListener;
use LioForumThreadsThreadDeleterListener;
use LioForumThreadsThreadForm;
use LioForumThreadsThreadRepository;
use LioForumThreadsThreadUpdaterListener;
use LioHttpControllersController;
use LioTagsTagRepository;
class ForumThreadsController extends Controller implements ThreadCreatorListener,ThreadUpdaterListener,ThreadDeleterListener
{
 protected $threads;
 protected $tags;
 protected $currentSection;
 protected $threadCreator;
 public function __construct(
  ThreadRepository $threads,ReplyRepository $replies,TagRepository $tags,ThreadCreator $threadCreator
 ) {
  $this->threads = $threads;
  $this->tags = $tags;
  $this->threadCreator = $threadCreator;
  $this->replies = $replies;
 }
}

注意构造函数中的几个类型约束,其实并没有地方实例化这个Controller并把这几个类型的参数传进去,Laravel会自动检测类的构造函数中的类型约束参数,并自动识别是否初始化并传入.PHP编程

源码vendor/illuminate/container/Container.php中的build办法:PHP编程

$constructor = $reflector->getConstructor();
dump($constructor);

这里会解析类的构造函数,在这里打印看:PHP编程

PHP编程

它会找出构造函数的参数,再看完整的build办法进行的操作:PHP编程

public function build($concrete,array $parameters = [])
{
 // If the concrete type is actually a Closure,we will just execute it and
 // hand back the results of the functions,which allows functions to be
 // used as resolvers for more fine-tuned resolution of these objects.
 if ($concrete instanceof Closure) {
  return $concrete($this,$parameters);
 }
 $reflector = new ReflectionClass($concrete);
 // If the type is not instantiable,the developer is attempting to resolve
 // an abstract type such as an Interface of Abstract Class and there is
 // no binding registered for the abstractions so we need to bail out.
 if (! $reflector->isInstantiable()) {
  $message = "Target [$concrete] is not instantiable.";
  throw new BindingResolutionContractException($message);
 }
 $this->buildStack[] = $concrete;
 $constructor = $reflector->getConstructor();
 // If there are no constructors,that means there are no dependencies then
 // we can just resolve the instances of the objects right away,without
 // resolving any other types or dependencies out of these containers.
 if (is_null($constructor)) {
  array_pop($this->buildStack);
  return new $concrete;
 }
 $dependencies = $constructor->getParameters();
 // Once we have all the constructor's parameters we can create each of the
 // dependency instances and then use the reflection instances to make a
 // new instance of this class,injecting the created dependencies in.
 $parameters = $this->keyParametersByArgument(
  $dependencies,$parameters
 );
 $instances = $this->getDependencies(
  $dependencies,$parameters
 );
 array_pop($this->buildStack);
 return $reflector->newInstanceArgs($instances);
}

具体从容器中获取实例的办法:PHP编程

protected function resolveClass(ReflectionParameter $parameter)
{
 try {
  return $this->make($parameter->getClass()->name);
 }
 // If we can not resolve the class instance,we will check to see if the value
 // is optional,and if it is we will return the optional parameter value as
 // the value of the dependency,similarly to how we do this with scalars.
 catch (BindingResolutionContractException $e) {
  if ($parameter->isOptional()) {
   return $parameter->getDefaultValue();
  }
  throw $e;
 }
}

框架底层通过Reflection反射为开发节省了很多细节,实现了自动依赖注入.这里不做继续深入研究了.PHP编程

写了一个模拟这个过程的类测试:PHP编程

<?php
class kulou
{
 //
}
class junjun
{
 //
}
class tanteng
{
 private $kulou;
 private $junjun;
 public function __construct(kulou $kulou,junjun $junjun)
 {
  $this->kulou = $kulou;
  $this->junjun = $junjun;
 }
}
//$tanteng = new tanteng(new kulou(),new junjun());
$reflector = new ReflectionClass('tanteng');
$constructor = $reflector->getConstructor();
$dependencies = $constructor->getParameters();
print_r($dependencies);exit;

原理是通过ReflectionClass类解析类的构造函数,并且取出构造函数的参数,从而判断依赖关系,从容器中取,并自动注入.PHP编程

转自:小谈博客 http://www.tantengvip.com/2016/01/laravel-construct-ioc/PHP编程

更多关于Laravel相关内容感兴趣的读者可查看本站专题:《Laravel框架入门与进阶教程》、《php优秀开发框架总结》、《smarty模板入门基础教程》、《php日期与时间用法总结》、《php面向对象程序设计入门教程》、《php字符串(string)用法总结》、《php+mysql数据库操作入门教程》及《php常见数据库操作技巧汇总》PHP编程

希望本文所述对大家基于Laravel框架的PHP程序设计有所赞助.PHP编程

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