Laravel實現建構函式自動依賴注入的方法，laravel建構函式_PHP教程

Laravel實現建構函式自動依賴注入的方法，laravel建構函式

本文執行個體講述了Laravel實現建構函式自動依賴注入的方法。分享給大家供大家參考，具體如下：

在Laravel的建構函式中可以實現自動依賴注入，而不需要執行個體化之前先執行個體化需要的類，如代碼所示：

<?phpnamespace 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; }}

注意建構函式中的幾個類型約束，其實並沒有地方執行個體化這個Controller並把這幾個類型的參數傳進去，Laravel會自動檢測類的建構函式中的類型約束參數，並自動識別是否初始化並傳入。

源碼vendor/illuminate/container/Container.php中的build方法：

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

這裡會解析類的建構函式，在這裡列印看：

它會找出建構函式的參數，再看完整的build方法進行的操作：

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);}

具體從容器中擷取執行個體的方法：

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; }}

架構底層通過Reflection反射為開發節省了很多細節，實現了自動依賴注入。這裡不做繼續深入研究了。

寫了一個類比這個過程的類測試：

<?phpclass 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;

原理是通過ReflectionClass類解析類的建構函式，並且取出建構函式的參數，從而判斷依賴關係，從容器中取，並自動注入。

轉自：小談部落格 http://www.tantengvip.com/2016/01/laravel-construct-ioc/

更多關於Laravel相關內容感興趣的讀者可查看本站專題：《Laravel架構入門與進階教程》、《php優秀開發架構總結》、《smarty模板入門基礎教程》、《php日期與時間用法總結》、《php物件導向程式設計入門教程》、《php字串(string)用法總結》、《php+mysql資料庫操作入門教程》及《php常見資料庫操作技巧匯總》

希望本文所述對大家基於Laravel架構的PHP程式設計有所協助。

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