本文实例讲述了Laravel实现html' target='_blank'>构造函数自动依赖注入的方法。分享给大家供大家参考，具体如下：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：namespace Lio/Http/Controllers/Forum;use Lio/Forum/Replies/ReplyRepository;use Lio/Forum/Threads/ThreadCreator;use Lio/Forum/Threads/ThreadCreatorListener;use Lio/Forum/Threads/ThreadDeleterListener;use Lio/Forum/Threads/ThreadForm;use Lio/Forum/Threads/ThreadRepository;use Lio/Forum/Threads/ThreadUpdaterListener;use Lio/Http/Controllers/Controller;use Lio/Tags/TagRepository;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 = $replies;注意构造函数中的几个类型约束，其实并没有地方实例化这个Controller并把这几个类型的参数传进去，Laravel会自动检测类的构造函数中的类型约束参数，并自动识别是否初始化并传入。源码vendor/illuminate/container/Container.php中的build方法：$constructor = $reflector- getConstructor();dump($constructor);这里会解析类的构造函数，在这里打印看：它会找出构造函数的参数，再看完整的build方法进行的操作：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方法：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。写了一个模拟这个过程的类测试：class kulouclass junjunclass 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。转自：小谈博客 http://www.tantengvip.com/2016/01/laravel-construct-ioc/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》希望本文所述对大家基于Laravel框架的PHP程序设计有所帮助。PHP教程
