Php 如何使用数据映射器模式延迟加载子对象?
如果我有一个相当复杂的用户模型,我想使用数据映射模式来加载它,那么我如何在不让用户知道UserMapper的情况下懒洋洋地加载一些更密集的用户信息呢 例如,如果用户模型允许一个地址对象数组(用户可能有很多地址对象,但不一定需要提前),那么如果需要,我将如何加载这些对象 我是否让用户模型知道AddressMapper 我是否将用户模型传递回UserMapper,然后UserMapper将只包含地址Php 如何使用数据映射器模式延迟加载子对象?,php,lazy-loading,datamapper,Php,Lazy Loading,Datamapper,如果我有一个相当复杂的用户模型,我想使用数据映射模式来加载它,那么我如何在不让用户知道UserMapper的情况下懒洋洋地加载一些更密集的用户信息呢 例如,如果用户模型允许一个地址对象数组(用户可能有很多地址对象,但不一定需要提前),那么如果需要,我将如何加载这些对象 我是否让用户模型知道AddressMapper 我是否将用户模型传递回UserMapper,然后UserMapper将只包含地址 有更好的选择吗?好吧,我曾经发现了以下聪明的模式,感谢Zend框架的开发人员。事情是这样的: cla
有更好的选择吗?好吧,我曾经发现了以下聪明的模式,感谢Zend框架的开发人员。事情是这样的:
class ModelRelation
implements IteratorAggregate
{
protected $_iterator;
protected $_mapper;
protected $_method;
protected $_arguments;
public function __construct( MapperAbstract $mapper, $method, array $arguments = array() )
{
$this->_mapper = $mapper;
$this->_method = $method;
$this->_arguments = $arguments;
}
public function getIterator()
{
if( $this->_iterator === null )
{
$this->_iterator = call_user_func_array( array( $this->_mapper, $this->_method ), $this->_arguments );
}
return $this->_iterator;
}
public function __call( $name, array $arguments )
{
return call_user_func_array( array( $this->getIterator(), $name ), $arguments );
}
}
class UserMapper
extends MapperAbstract
{
protected $_addressMapper;
public function __construct( AddressMapper $addressMapper )
{
$this->_addressMapper = $addressMapper;
}
public function getUserById( $id )
{
$userData = $this->getUserDataSomehow();
$user = new User( $userData );
$user->addresses = new ModelRelation(
$this->_addressesMapper,
'getAddressesByUserId',
array( $id )
);
return $user;
}
}
class AddressMapper
extends MapperAbstract
{
public function getAddressesByUserId( $id )
{
$addressData = $this->getAddressDataSomehow();
$addresses = new SomeAddressIterator( $addressData );
return $addresses;
}
}
$user = $userMapper->getUserById( 3 );
foreach( $user->addresses as $address ) // calls getIterator() of ModelRelation
{
// whatever
}
Ben Scholzen的实际实施
您使用它的方式如下:
class ModelRelation
implements IteratorAggregate
{
protected $_iterator;
protected $_mapper;
protected $_method;
protected $_arguments;
public function __construct( MapperAbstract $mapper, $method, array $arguments = array() )
{
$this->_mapper = $mapper;
$this->_method = $method;
$this->_arguments = $arguments;
}
public function getIterator()
{
if( $this->_iterator === null )
{
$this->_iterator = call_user_func_array( array( $this->_mapper, $this->_method ), $this->_arguments );
}
return $this->_iterator;
}
public function __call( $name, array $arguments )
{
return call_user_func_array( array( $this->getIterator(), $name ), $arguments );
}
}
class UserMapper
extends MapperAbstract
{
protected $_addressMapper;
public function __construct( AddressMapper $addressMapper )
{
$this->_addressMapper = $addressMapper;
}
public function getUserById( $id )
{
$userData = $this->getUserDataSomehow();
$user = new User( $userData );
$user->addresses = new ModelRelation(
$this->_addressesMapper,
'getAddressesByUserId',
array( $id )
);
return $user;
}
}
class AddressMapper
extends MapperAbstract
{
public function getAddressesByUserId( $id )
{
$addressData = $this->getAddressDataSomehow();
$addresses = new SomeAddressIterator( $addressData );
return $addresses;
}
}
$user = $userMapper->getUserById( 3 );
foreach( $user->addresses as $address ) // calls getIterator() of ModelRelation
{
// whatever
}
事情是这样的;如果对象图在某一点变得非常复杂和嵌套很深,这可能会变得非常缓慢,因为映射程序都必须查询自己的数据(假定您使用数据库进行持久化)。当我将此模式用于CMS以获取嵌套的页面
对象(任意深度的子页面)时,我遇到了这种情况
它可能会被一些缓存机制调整,以大大加快速度