Laravel implement the method of automatic dependency injection of constructors, Laravel constructor _php tutorial

Laravel implements the method of automatic dependency injection of constructors, Laravel constructor

This paper describes the method of laravel implementation of automatic dependency injection of constructors. Share to everyone for your reference, as follows:

Automatic dependency injection can be implemented in the constructor of Laravel without the need to instantiate the class before instantiating it, as shown in the code:

<?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 $threadC  Reator) {$this->threads = $threads;  $this->tags = $tags;  $this->threadcreator = $threadCreator; $this->replies = $replies; }}

Note that there are several types of constraints in the constructor, and there is no place to instantiate the controller and pass these types of arguments in, Laravel automatically detects the type constraint parameters in the class's constructor and automatically recognizes whether to initialize and pass in.

The build method in source vendor/illuminate/container/container.php:

$constructor = $reflector->getconstructor ();d UMP ($constructor);

This resolves the constructor of the class, which is printed here:

It will find out the parameters of the constructor, and then see the complete build method for the operation:

Public function build ($concrete, array $parameters = []) {//If the concrete type is actually a Closure, we'll just exec Ute it and//hand back the results of the functions, which allows functions to being//used as resolvers for more fine-tune D resolution of these objects. if ($concrete instanceof Closure) {return $concrete ($this, $parameters);} $reflector = new Reflectionclass ($concrete); If the type is not instantiable, the developer are attempting to resolve//a abstract type such as an Interface of Abs Tract Class and there are//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 = $reflector->getconstructor (); If There is no constructors, that means there is no dependencies then//We can just resolve the instances of the obj ECTs right away, withoutResolving any and types or dependencies out of these containers.  if (Is_null ($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 Reflec tion instances to make a//new instance of this class, injecting the created dependencies in. $parameters = $this->key Parametersbyargument ($dependencies, $parameters); $instances = $this->getdependencies ($dependencies, $parameters); Array_pop ($this->buildstack); Return $reflector->newinstanceargs ($instances);}

How to get an instance from a container specifically:

protected function Resolveclass (Reflectionparameter $parameter) {try {  return $this->make ($parameter- GetClass ()->name); }//If we can not resolve the class instance, we'll check to see If the value//are optional, and if it is we'll retu RN 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; }}

The bottom layer of the frame is developed by reflection reflection to save a lot of detail and realize automatic dependency injection. There's no further research here.

Write a class test that simulates the process:

<?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 = $constructor->getparameters ();p rint_r ($dependencies); exit;

The principle is to parse the constructor of the class through the Reflectionclass class and take out the parameters of the constructor to determine the dependency, fetch from the container, and inject it automatically.

Turn from: Small Talk blog http://www.tantengvip.com/2016/01/laravel-construct-ioc/

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It is hoped that this article is helpful to the PHP program design based on Laravel framework.

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