PHP进阶学习之依赖注入与Ioc容器详解

<?php
class IoC
{
  protected static $registry = [];
  public static function bind($name, Callable $resolver) //传入类名和类对象实例
  {
    static::$registry[$name] = $resolver;
  }
  public static function make($name) //静态工厂方法
  {
    if (isset(static::$registry[$name])) {
      $resolver = static::$registry[$name];
      return $resolver(); //实例化
    }
    throw new Exception('Alias does not exist in the IoC registry.');
  }
}

<?php //依赖关系：Company->Department->Group
class Group
{
  public function doSomething()
  {
    echo __CLASS__.":".'hello', '|';
  }
}
class Department
{
  private $group;
  public function __construct(Group $group)
  {
    $this->group = $group;
  }
  public function doSomething()
  {
    $this->group->doSomething();
    echo __CLASS__.":".'hello', '|';
  }
}
class Company
{
  private $department;
  public function __construct(Department $department)
  {
    $this->department = $department;
  }
  public function doSomething()
  {
    $this->department->doSomething();
    echo __CLASS__.":".'hello', '|';
  }
}

<?php
class Container
{
  private $s = array();
  public function __set($k, $c)
  {
    $this->s[$k] = $c;
  }
  public function __get($k)
  {
    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)
  {
    // 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);
    }
    /*通过反射获取类的内部结构，实例化类*/
    $reflector = new ReflectionClass($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()) {
      return $parameter->getDefaultValue();
    }
    throw new Exception('I have no idea what to do here.');
  }
}
require_once "./testclass.php"; //开始测试，先测试已知依赖关系的情况
$c = new Container();
$c->department = 'Department';
$c->company = function ($c) {
  return new Company($c->department);
};
// 从容器中取得company
$company = $c->company;
$company->doSomething(); //输出: Group:hello|Department:hello|Company:hello|
// 测试未知依赖关系，直接使用的方法
$di = new Container();
$di->company = 'Company';
$company = $di->company;
$company->doSomething();//输出: Group:hello|Department:hello|Company:hello|