PHP進(jìn)階學(xué)習(xí)之依賴注入與Ioc容器詳解

?php
class IoC
{
  protected static $registry = [];
  public static function bind($name, Callable $resolver) //傳入類名和類對(duì)象實(shí)例
  {
    static::$registry[$name] = $resolver;
  }
  public static function make($name) //靜態(tài)工廠方法
  {
    if (isset(static::$registry[$name])) {
      $resolver = static::$registry[$name];
      return $resolver(); //實(shí)例化
    }
    throw new Exception('Alias does not exist in the IoC registry.');
  }
}

?php //依賴關(guān)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]);
  }
  /**
   * 自動(dòng)綁定（Autowiring）自動(dòng)解析（Automatic Resolution）
   *
   * @param string $className
   * @return object
   * @throws Exception
   */
  public function build($className)
  {
    // 如果是匿名函數(shù)（Anonymous functions），也叫閉包函數(shù)（closures）
    if ($className instanceof Closure) {
      // 執(zhí)行閉包函數(shù)，并將結(jié)果
      return $className($this);
    }
    /*通過反射獲取類的內(nèi)部結(jié)構(gòu)，實(shí)例化類*/
    $reflector = new ReflectionClass($className);
    // 檢查類是否可實(shí)例化, 排除抽象類abstract和對(duì)象接口interface
    if (!$reflector->isInstantiable()) {
      throw new Exception("Can't instantiate this.");
    }
    /** @var ReflectionMethod $constructor 獲取類的構(gòu)造函數(shù) */
    $constructor = $reflector->getConstructor();
    // 若無構(gòu)造函數(shù)，直接實(shí)例化并返回
    if (is_null($constructor)) {
      return new $className;
    }
    // 取構(gòu)造函數(shù)參數(shù),通過 ReflectionParameter 數(shù)組返回參數(shù)列表
    $parameters = $constructor->getParameters();
    // 遞歸解析構(gòu)造函數(shù)的參數(shù)
    $dependencies = $this->getDependencies($parameters);
    // 創(chuàng)建一個(gè)類的新實(shí)例，給出的參數(shù)將傳遞到類的構(gòu)造函數(shù)。
    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)) {
        // 是變量,有默認(rèn)值則設(shè)置默認(rèn)值
        $dependencies[] = $this->resolveNonClass($parameter);
      } else {
        // 是一個(gè)類，遞歸解析
        $dependencies[] = $this->build($dependency->name);
      }
    }
    return $dependencies;
  }
  /**
   * @param ReflectionParameter $parameter
   * @return mixed
   * @throws Exception
   */
  public function resolveNonClass($parameter)
  {
    // 有默認(rèn)值則返回默認(rèn)值
    if ($parameter->isDefaultValueAvailable()) {
      return $parameter->getDefaultValue();
    }
    throw new Exception('I have no idea what to do here.');
  }
}
require_once "./testclass.php"; //開始測(cè)試，先測(cè)試已知依賴關(guān)系的情況
$c = new Container();
$c->department = 'Department';
$c->company = function ($c) {
  return new Company($c->department);
};
// 從容器中取得company
$company = $c->company;
$company->doSomething(); //輸出: Group:hello|Department:hello|Company:hello|
// 測(cè)試未知依賴關(guān)系，直接使用的方法
$di = new Container();
$di->company = 'Company';
$company = $di->company;
$company->doSomething();//輸出: Group:hello|Department:hello|Company:hello|