Implementation of lazy loading

In order to implement lazy loading, Orient has implemented some sort of metaprogramming when hydrating objects.

At run-time, when the Mapper hydrates a record of class User:

use Congow\Orient\ODM\Mapper\Annotations\Property;

class User
{
  /**
   * Property(type="link")
   */
  protected $address;

   public function setAddress(Address $address)
   {
     $this->address = $address;
   }

   public function getAddress()
   {
     return $this->address;
   }
}

it returns an object of type UserProxy, making it possible to retrieve a record and its associated records lazily.

A proxy is, basically, a class which extends all the public methods of a record class and checks if a property is returned as an object of type Congow\Orient\ODM\Proxy\AbstractProxy, which means that it should contain an object with the logic of retrieving a record.

Proxies look like:

class AddressProxy extends Address
{
  public function getType()
  {
    $parent = parent::getType();

    if (!is_null($parent)) {
        if ($parent instanceOf \Congow\Orient\ODM\Proxy\AbstractProxy) {
            return $parent();
        }

        return $parent;
    }
  }
}

Objects of type AbstractProxy, when called as functions through PHP’s magic __invoke() method, contain the business logic to do a query and retrieve the related record(s):

public function __invoke()
{
  return $mapper->find($rid);
}

Proxies are created once you hydrate an object of class X ( XProxy ): they are never automatically re-generated, so you’ll need to delete the proxy classes once you modify a public method of the X class.

To set the directory in which you’re going to generate proxies you only need to do a couple things: first, you need to setup the autoloader:

$classLoader = new SplClassLoader('Congow\Orient\Proxy', "/abs/path/to/proxies");
$classLoader->register();

then, once you instantiate a Mapper, you nedd to pass it the proxies directory:

$mapper = new Mapper($adapter, "/abs/path/to/proxies")

Remember to create, under /abs/path/to/proxies, the subdirectories:

Congow
|
|_ Orient
  |
  |_ Proxy

because proxies will be autoloaded in /abs/path/to/proxies/Congow/Orient/Proxy directory.

A final hint, if you are using a caching system in your software, you may want to put the proxies there.

In Symfony2, for example, a good location for proxies might be app/cache.