Laravel容器----依赖注入【部分源码】

<?php

class Container
{
	protected $bindings = [];
	// bind用于绑定或者注册服务
	public function bind($abstract, $concrete = null, $shared = false) {
		if (! $concrete instanceof Closure) {
			$concrete = $this->getClosure($abstract, $concrete);
		}
		$this->bindings[$abstract] = compact('concrete', 'shared');
	}

	// 为没提供闭包函数的服务提供一个默认的闭包
	protected function getClosure($abstract, $concrete) {
		return function ($c) use ($abstract, $concrete) {
			$method = ($abstract == $concrete) ? 'build' : 'make';
			return $c->$method($concrete);
		};
	}

	// 生成实例
	public function make($abstract) {
		$concrete = $this->getConcrete($abstract);
		if ($this->isBuildable($abstract, $concrete)) {
			return $this->build($concrete);
		}
		return $this->make($concrete);
	}

	// 生成实例
	public function build($concrete) {
		if ($concrete instanceof Closure) {
			return $concrete($this);
		}

		$reflection = new ReflectionClass($concrete);
		if (!$reflection->isInstantiable()) {
			echo $message = 'This class is not instantiable !!!!';
			return;
		}
		$constructor = $reflection->getConstructor();
		if (is_null($constructor)) {
			return new $concrete;
		}

		$dependencies = $constructor->getParameters();
		$parameters = $this->resolveDependencies($dependencies);
		return $reflection->newInstanceArgs($parameters);
	}

	// 解决参数依赖
	protected function resolveDependencies($parameters) {
		$dependencies = null;
		foreach ($parameters as $parameter) {
			$_cls = $parameter->getClass();
			if (is_null($_cls)) {
				$dependencies[] = null;
			} else {
				$dependencies[] = $this->make($_cls->name);
			}
		}
		return (array) $dependencies;
	}

	protected function isBuildable($abstract, $concrete) {
		return $abstract == $concrete || $concrete instanceof Closure;
	}

	protected function getConcrete($abstract) {
		if (!isset($this->bindings[$abstract])) {
			return $abstract;
		}
		return $this->bindings[$abstract]['concrete'];
	}
}

// test code part
Interface A {
	public function test();
}

class B implements A {
	public function test(){
		echo 'This is b from A';
	}
}

class C implements A {
	public function __construct($name){
		$this->name = $name;
	}

	public function test(){
		echo 'This is c from A';
	}
}

class D {
	public $obj;

	/**
	 * D constructor.
	 * @param $obj
	 */
	public function __construct(A $obj)
	{
		$this->obj = $obj;
	}


	public function run() {
		$this->obj->test();
	}
}

$app = new Container();
$app->bind('A', 'C');
$app->bind('D', 'D');
$d = $app->make('D');
$d->run();