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859天前/** |
* Subject interface. |
* Client depends only on this abstraction. |
*/ |
interface Image { |
public function getWidth(); |
public function getHeight(); |
public function getPath(); |
/** |
* @return string the image's byte stream |
*/ |
public function dump(); |
} |
/** |
* Abstract class to avoid repetition of boilerplate code in the Proxy |
* and in the Subject. Only the methods which can be provided without |
* instancing the RealSubject are present here. |
*/ |
abstract class AbstractImage implements Image { |
protected $_width; |
protected $_height; |
protected $_path; |
protected $_data; |
public function getWidth() { |
return $this->_width; |
} |
public function getHeight() { |
return $this->_height; |
} |
public function getPath() { |
return $this->_path; |
} |
} |
/** |
* The RealSubject. Always loads the image, even if no dump of the data |
* is required. |
*/ |
class RawImage extends AbstractImage { |
public function __construct ($path) { |
$this->_path = $path; |
list ($this->_width, $this->_height) = getimagesize ($path); |
$this->_data = file_get_contents ($path); |
} |
public function dump() { |
return $this->_data; |
} |
} |
/** |
* Proxy. Defers loading the image data until it becomes really mandatory. |
* This class does its best to postpone the very expensive operations |
* such as the actual loading of the BLOB. |
*/ |
class ImageProxy extends AbstractImage { |
public function __construct ($path) { |
$this->_path = $path; |
list ($this->_width, $this->_height) = getimagesize ($path); |
} |
/** |
* Creates a RawImage and exploits its functionalities. |
*/ |
protected function _lazyLoad() { |
if ($this->_realImage == = null) { |
$this->_realImage = new RawImage ($this->_path); |
} |
} |
public function dump() { |
$this->_lazyLoad(); |
return $this->_realImage->dump(); |
} |
} |
/** |
* Client class that does not use the data dump of the image. |
* Passing blindly a Proxy to this class and to other Clients makes sense |
* as the data would be loaded anyway when Image::dump() is called. |
*/ |
class Client { |
public function tag (Image $img) { |
return '; |
} |
} |
$path = ' / home / giorgio / shared / Immagini / kiki.png'; |
$client = new Client(); |
$image = new RawImage($path); // loading of the BLOB takes place |
echo $client->tag($image), "\n"; |
$proxy = new ImageProxy($path); |
echo $client->tag($proxy), "\n"; // loading does not take place even here |
