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今天就跟大家聊聊有关怎么在Laravel中实现一个构造函数自动依赖注入功能，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。
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：
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：
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;看完上述内容，你们对怎么在Laravel中实现一个构造函数自动依赖注入功能有进一步的了解吗？如果还想了解更多知识或者相关内容，请关注创新互联行业资讯频道，感谢大家的支持。