laravel 依赖注入容器原理

class Bim
{
    public function doSomething()
    {
        echo __METHOD__, '|';
    }
}
 
class Bar
{
    private $bim;
 
    public function __construct(Bim $bim)
    {
        $this->bim = $bim;
    }
 
    public function doSomething()
    {
        $this->bim->doSomething();
        echo __METHOD__, '|';
    }
}
 
class Foo
{
    private $bar;
 
    public function __construct(Bar $bar)
    {
        $this->bar = $bar;
    }
 
    public function doSomething()
    {
        $this->bar->doSomething();
        echo __METHOD__;
    }
}
 
class Container
{
    private $s = array();
 
    public function __set($k, $c)
    {
        $this->s[$k] = $c;
    }
 
    public function __get($k)
    {
        // return $this->s[$k]($this);
        return $this->build($this->s[$k]);
    }
 
    /**
     * 自动绑定（Autowiring）自动解析（Automatic Resolution）
     *
     * @param string $className
     * @return object
     * @throws Exception
     */
    public function build($className)
    {
        echo "<pre>";var_dump($className);
        // 如果是匿名函数（Anonymous functions），也叫闭包函数（closures）
        if ($className instanceof Closure) {
            // 执行闭包函数，并将结果
            return $className($this);
        }
 
        /** @var ReflectionClass $reflector */
        $reflector = new ReflectionClass($className);
 
        // 检查类是否可实例化, 排除抽象类abstract和对象接口interface
        if (!$reflector->isInstantiable()) {
            throw new Exception("Can't instantiate this.");
        }
 
        /** @var ReflectionMethod $constructor 获取类的构造函数 */
        $constructor = $reflector->getConstructor();
 
        // 若无构造函数，直接实例化并返回
        if (is_null($constructor)) {
            return new $className;
        }
 
        // 取构造函数参数,通过 ReflectionParameter 数组返回参数列表
        $parameters = $constructor->getParameters();
 
        // 递归解析构造函数的参数
        $dependencies = $this->getDependencies($parameters);
 
 
        // 创建一个类的新实例，给出的参数将传递到类的构造函数。
        return $reflector->newInstanceArgs($dependencies);
    }
 
    /**
     * @param array $parameters
     * @return array
     * @throws Exception
     */
    public function getDependencies($parameters)
    {
        $dependencies = [];
 
        /** @var ReflectionParameter $parameter */
        foreach ($parameters as $parameter) {
            /** @var ReflectionClass $dependency */
            $dependency = $parameter->getClass();
            if (is_null($dependency)) {
                // 是变量,有默认值则设置默认值
                $dependencies[] = $this->resolveNonClass($parameter);
            } else {
                // 是一个类，递归解析
                $dependencies[] = $this->build($dependency->name);
            }
        }
 
        return $dependencies;
    }
 
    /**
     * @param ReflectionParameter $parameter.
     * @return mixed
     * @throws Exception
     */
    public function resolveNonClass($parameter)
    {
        // 有默认值则返回默认值
        if ($parameter->isDefaultValueAvailable()) {
            var_dump(1);
            var_dump($parameter->getDefaultValue());
            return $parameter->getDefaultValue();
        }
 
        throw new Exception('I have no idea what to do here.');
    }
}
 
// ----
//$c = new Container();
//$c->bar = 'Bar';
//$c->foo = function ($c) {
//    return new Foo($c->bar);
//};
//// 从容器中取得Foo
//$foo = $c->foo;
//$foo->doSomething(); // Bim::doSomething|Bar::doSomething|Foo::doSomething
 
///*// ----
$di = new Container();
//
$di->foo = 'Foo';
//
///** @var Foo $foo */
$foo = $di->foo;
//
var_dump($foo);
echo "<pre>";var_dump($foo->doSomething());
 exit;
var_dump( get_class($foo));
die();
///*
//Foo#10 (1) {
//  private $bar =>
//  class Bar#14 (1) {
//    private $bim =>
//    class Bim#16 (0) {
//    }
//  }
//}
//*/
//
$foo->doSomething(); // Bim::doSomething|Bar::doSomething|Foo::doSomething*/