[PHP] php面试实现反射注入的详细方法

/**
 
 * Class Point
 
 */
 
class Point
 
{
 
 public $x;
 
 public $y;
 
 
 
 /**
 
 * Point constructor.
 
 * @param int $x horizontal value of point's coordinate
 
 * @param int $y vertical value of point's coordinate
 
 */
 
 public function __construct($x = 0, $y = 0)
 
 {
 
 $this->x = $x;
 
 $this->y = $y;
 
 }
 
}

class Circle
 
{
 
 /**
 
 * @var int
 
 */
 
 public $radius;//半径
 
 
 
 /**
 
 * @var Point
 
 */
 
 public $center;//圆心点
 
 
 
 const PI = 3.14;
 
 
 
 public function __construct(Point $point, $radius = 1)
 
 {
 
 $this->center = $point;
 
 $this->radius = $radius;
 
 }
 
 
 
 //打印圆点的坐标
 
 public function printCenter()
 
 {
 
 printf('center coordinate is (%d, %d)', $this->center->x, $this->center->y);
 
 }
 
 
 
 //计算圆形的面积
 
 public function area()
 
 {
 
 return 3.14 * pow($this->radius, 2);
 
 }
 
}

$reflectionClass = new reflectionClass(Circle::class);
 
//返回值如下
 
object(ReflectionClass)#1 (1) {
 
 ["name"]=>
 
 string(6) "Circle"
 
}

$reflectionClass->getConstants();

array(1) {
 
 ["PI"]=>
 
 float(3.14)
 
}

$reflectionClass->getProperties();

array(3) {
 
 [0]=>
 
 object(ReflectionMethod)#2 (2) {
 
 ["name"]=>
 
 string(11) "__construct"
 
 ["class"]=>
 
 string(6) "Circle"
 
 }
 
 [1]=>
 
 object(ReflectionMethod)#3 (2) {
 
 ["name"]=>
 
 string(11) "printCenter"
 
 ["class"]=>
 
 string(6) "Circle"
 
 }
 
 [2]=>
 
 object(ReflectionMethod)#4 (2) {
 
 ["name"]=>
 
 string(4) "area"
 
 ["class"]=>
 
 string(6) "Circle"
 
 }
 
}

$constructor = $reflectionClass->getConstructor();

$parameters = $constructor->getParameters();

array(2) {
 
 [0]=>
 
 object(ReflectionParameter)#3 (1) {
 
 ["name"]=>
 
 string(5) "point"
 
 }
 
 [1]=>
 
 object(ReflectionParameter)#4 (1) {
 
 ["name"]=>
 
 string(6) "radius"
 
 }
 
}

//构建类的对象
 
function make($className)
 
{
 
 $reflectionClass = new ReflectionClass($className);
 
 $constructor = $reflectionClass->getConstructor();
 
 $parameters = $constructor->getParameters();
 
 $dependencies = getDependencies($parameters);
 
  
 
 return $reflectionClass->newInstanceArgs($dependencies);
 
}
 
 
 
//依赖解析
 
function getDependencies($parameters)
 
{
 
 $dependencies = [];
 
 foreach($parameters as $parameter) {
 
  $dependency = $parameter->getClass();
 
  if (is_null($dependency)) {
 
   if($parameter->isDefaultValueAvailable()) {
 
  $dependencies[] = $parameter->getDefaultValue();
 
   } else {
 
  //不是可选参数的为了简单直接赋值为字符串0
 
  //针对构造方法的必须参数这个情况
 
  //laravel是通过service provider注册closure到IocContainer,
 
  //在closure里可以通过return new Class($param1, $param2)来返回类的实例
 
  //然后在make时回调这个closure即可解析出对象
 
  //具体细节我会在另一篇文章里面描述
 
  $dependencies[] = '0';
 
   }
 
  } else {
 
   //递归解析出依赖类的对象
 
   $dependencies[] = make($parameter->getClass()->name);
 
  }
 
 }
 
 
 
 return $dependencies;
 
}

$circle = make('Circle');
 
$area = $circle->area();
 
/*var_dump($circle, $area);
 
object(Circle)#6 (2) {
 
 ["radius"]=>
 
 int(1)
 
 ["center"]=>
 
 object(Point)#11 (2) {
 
 ["x"]=>
 
 int(0)
 
 ["y"]=>
 
 int(0)
 
 }
 
}
 
float(3.14)*/