PHP 종속성 주입 컨테이너 시리즈 이해(2) 필요한 것

$storage = new SessionStorage('SESSION_ID');
$user = new User($storage);

$transport = new Zend_Mail_Transport_Smtp('smtp.gmail.com', array(
  'auth'     => 'login',
  'username' => 'foo',
  'password' => 'bar',
  'ssl'      => 'ssl',
  'port'     => 465,
));
$mailer = new Zend_Mail();
$mailer->setDefaultTransport($transport);

class Container
{
  public function getMailTransport()
  {
    return new Zend_Mail_Transport_Smtp('smtp.gmail.com', array(
      'auth'     => 'login',
      'username' => 'foo',
      'password' => 'bar',
      'ssl'      => 'ssl',
      'port'     => 465,
    ));
  }
  public function getMailer()
  {
    $mailer = new Zend_Mail();
    $mailer->setDefaultTransport($this->getMailTransport());
    return $mailer;
  }
}
//容器的使用也很简单
$container = new Container();
$mailer = $container->getMailer();

class Container
{
  protected $parameters = array();
  public function __construct(array $parameters = array())
  {
    $this->parameters = $parameters;
  }
  public function getMailTransport()
  {
    return new Zend_Mail_Transport_Smtp('smtp.gmail.com', array(
      'auth'     => 'login',
      'username' => $this->parameters['mailer.username'],
      'password' => $this->parameters['mailer.password'],
      'ssl'      => 'ssl',
      'port'     => 465,
    ));
  }
  public function getMailer()
  {
    $mailer = new Zend_Mail();
    $mailer->setDefaultTransport($this->getMailTransport());
    return $mailer;
  }
}

$container = new Container(array(
  'mailer.username' => 'foo',
  'mailer.password' => 'bar',
));
$mailer = $container->getMailer();

class Container
{
  // ...
  public function getMailer()
  {
    $class = $this->parameters['mailer.class'];
    $mailer = new $class();
    $mailer->setDefaultTransport($this->getMailTransport());
    return $mailer;
  }
}
$container = new Container(array(
  'mailer.username' => 'foo',
  'mailer.password' => 'bar',
  'mailer.class'    => 'MyTest_Mail',
));
$mailer = $container->getMailer();

class Container
{
  static protected $shared = array();
  // ...
  public function getMailer()
  {
    if (isset(self::$shared['mailer']))
    {
      return self::$shared['mailer'];
    }
    $class = $this->parameters['mailer.class'];
    $mailer = new $class();
    $mailer->setDefaultTransport($this->getMailTransport());
    return self::$shared['mailer'] = $mailer;
  }
}