2.5. Decorator¶
2.5.1. Purpose¶
To dynamically add new functionality to class instances.
2.5.2. Examples¶
- Zend Framework: decorators for
Zend_Form_Element
instances - Web Service Layer: Decorators JSON and XML for a REST service (in this case, only one of these should be allowed of course)
2.5.3. UML Diagram¶
2.5.4. Code¶
You can also find these code on GitHub
RendererInterface.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | <?php
namespace DesignPatterns\Structural\Decorator;
/**
* Class RendererInterface
*/
interface RendererInterface
{
/**
* render data
*
* @return mixed
*/
public function renderData();
}
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Webservice.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | <?php
namespace DesignPatterns\Structural\Decorator;
/**
* Class Webservice
*/
class Webservice implements RendererInterface
{
/**
* @var mixed
*/
protected $data;
/**
* @param mixed $data
*/
public function __construct($data)
{
$this->data = $data;
}
/**
* @return string
*/
public function renderData()
{
return $this->data;
}
}
|
Decorator.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | <?php
namespace DesignPatterns\Structural\Decorator;
/**
* the Decorator MUST implement the RendererInterface contract, this is the key-feature
* of this design pattern. If not, this is no longer a Decorator but just a dumb
* wrapper.
*/
/**
* class Decorator
*/
abstract class Decorator implements RendererInterface
{
/**
* @var RendererInterface
*/
protected $wrapped;
/**
* You must type-hint the wrapped component :
* It ensures you can call renderData() in the subclasses !
*
* @param RendererInterface $wrappable
*/
public function __construct(RendererInterface $wrappable)
{
$this->wrapped = $wrappable;
}
}
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RenderInXml.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | <?php
namespace DesignPatterns\Structural\Decorator;
/**
* Class RenderInXml
*/
class RenderInXml extends Decorator
{
/**
* render data as XML
*
* @return mixed|string
*/
public function renderData()
{
$output = $this->wrapped->renderData();
// do some fancy conversion to xml from array ...
$doc = new \DOMDocument();
foreach ($output as $key => $val) {
$doc->appendChild($doc->createElement($key, $val));
}
return $doc->saveXML();
}
}
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RenderInJson.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | <?php
namespace DesignPatterns\Structural\Decorator;
/**
* Class RenderInJson
*/
class RenderInJson extends Decorator
{
/**
* render data as JSON
*
* @return mixed|string
*/
public function renderData()
{
$output = $this->wrapped->renderData();
return json_encode($output);
}
}
|
2.5.5. Test¶
Tests/DecoratorTest.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 | <?php
namespace DesignPatterns\Structural\Decorator\Tests;
use DesignPatterns\Structural\Decorator;
/**
* DecoratorTest tests the decorator pattern
*/
class DecoratorTest extends \PHPUnit_Framework_TestCase
{
protected $service;
protected function setUp()
{
$this->service = new Decorator\Webservice(array('foo' => 'bar'));
}
public function testJsonDecorator()
{
// Wrap service with a JSON decorator for renderers
$service = new Decorator\RenderInJson($this->service);
// Our Renderer will now output JSON instead of an array
$this->assertEquals('{"foo":"bar"}', $service->renderData());
}
public function testXmlDecorator()
{
// Wrap service with a JSON decorator for renderers
$service = new Decorator\RenderInXml($this->service);
// Our Renderer will now output XML instead of an array
$xml = '<?xml version="1.0"?><foo>bar</foo>';
$this->assertXmlStringEqualsXmlString($xml, $service->renderData());
}
/**
* The first key-point of this pattern :
*/
public function testDecoratorMustImplementsRenderer()
{
$className = 'DesignPatterns\Structural\Decorator\Decorator';
$interfaceName = 'DesignPatterns\Structural\Decorator\RendererInterface';
$this->assertTrue(is_subclass_of($className, $interfaceName));
}
/**
* Second key-point of this pattern : the decorator is type-hinted
*
* @expectedException \PHPUnit_Framework_Error
*/
public function testDecoratorTypeHinted()
{
$this->getMockForAbstractClass('DesignPatterns\Structural\Decorator\Decorator', array(new \stdClass()));
}
/**
* The decorator implements and wraps the same interface
*/
public function testDecoratorOnlyAcceptRenderer()
{
$mock = $this->getMock('DesignPatterns\Structural\Decorator\RendererInterface');
$dec = $this->getMockForAbstractClass('DesignPatterns\Structural\Decorator\Decorator', array($mock));
$this->assertNotNull($dec);
}
}
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