本文实例讲述了PHP设计模式之装饰器(装饰者)模式(Decorator)入门与应用。分享给大家供大家参考,具体如下:
通常情况下,我们如果要给对象添加功能,要么直接修改对象添加相应的功能,要么派生对应的子类来扩展,抑或是使用对象组合的方式。显然,直接修改对应的类这种方式并不可取。
在面向对象的设计中,我们也应该尽量使用对象组合,而不是对象继承来扩展和复用功能。装饰器模式就是基于对象组合的方式,可以很灵活的给对象添加所需要的功能,并且它的本质就是动态组合,一句话,动态是手段,组合才是目的。
也就是说,在这种模式下,我们可以对已有对象的部分内容或者功能进行调整,但是不需要修改原始对象结构,理解了不???
还可以理解为,我们不去修改已有的类,而是通过创建另外一个装饰器类,通过这个装饰器类去动态的扩展其需要修改的内容。而它的好处也是显而易见的,如下:
我们来看下《PHP设计模式》里面的一个案例:
/** * 被修饰类 现在的需求: 要求能够动态为CD添加音轨、能显示CD音轨列表。 显示时应采用单行并且为每个音轨都以音轨好为前缀。 */ class CD { public $trackList; function __construct() { # code... $this->trackList=array(); } public function addTrack($track){ $this->trackList[]=$track; } public function getTrackList(){ $output=" "; foreach ($this->trackList as $key => $value) { # code... $output.=($key+1).") {$value}. "; } return $output; } } /* 现在需求发生变化: 要求将当前实例输出的音轨都采用大写形式。 这个需求并不是一个变化特别大的需求,不需要修改基类或创建一个父子关系的子类,此时创建一个基于装饰器模式的装饰器类。 */ class CDTrackListDecoratorCaps{ private $_cd; public function __construct(CD $CD){ $this->_cd=$CD; } public function makeCaps(){ foreach ($this->_cd->trackList as $key => $value) { # code... $this->_cd->trackList[$key]=strtoupper($value); //转换成大写 } } } //客户端测试 $myCD=new CD(); $trackList=array( "what It Means", "brr", "goodBye" ); foreach ($trackList as $key => $value) { # code... $myCD->addTrack($value); } $myCDCaps=new CDTrackListDecoratorCaps($myCD); $myCDCaps->makeCaps(); print "The CD contains the following tracks:".$myCD->getTrackList();
来看一个比较通俗但是比较简单的案例:
代码如下:
UserInfo.php
//装饰器模式,对已有对象的部分内容或者功能进行调整,但是不需要修改原始对象结构,可以使用装饰器设计模式 class UserInfo { public $userInfo = array(); public function addUser($userInfo) { $this->userInfo[] = $userInfo; } public function getUserList() { print_r($this->userInfo); } }
//UserInfoDecorate 装饰一样,改变用户信息输出为大写格式,不改变原先UserInfo类 <?php include("UserInfo.php"); class UserInfoDecorate { public function makeCaps($UserInfo) { foreach ($UserInfo->userInfo as &$val) { $val = strtoupper($val); } } } $UserInfo = new UserInfo; $UserInfo->addUser('zhu'); $UserInfo->addUser('initphp'); $UserInfoDecorate = new UserInfoDecorate; $UserInfoDecorate->makeCaps($UserInfo); $UserInfo->getUserList();
到此,咱们应该是对于装饰器模式有了一个大概的了解,接下来咱们看一下构建装饰器模式的案例,网上的,先来看目录结构:
|decorator #项目根目录
|--Think #核心类库
|----Loder.php #自动加载类
|----decorator.php #装饰器接口
|----colorDecorator.php #颜色装饰器
|----sizeDecorator.php #字体大小装饰器
|----echoText.php #被装饰者
|--index.php #单一的入口文件
完事就是来构建装饰器接口,Think/decorator.php,如下:
<?php /** * 装饰器接口 * Interface decorator * @package Think */ namespace Think; interface decorator{ public function beforeDraw(); public function afterDraw(); }
再来就是颜色装饰器 Think/colorDecorator.php,如下:
<?php /** * 颜色装饰器 */ namespace Think; class colorDecorator implements decorator{ protected $color; public function __construct($color) { $this->color = $color; } public function beforeDraw() { echo "color decorator :{$this->color}\n"; } public function afterDraw() { echo "end color decorator\n"; } }
还有就是字体大小装饰器 Think/sizeDecorator.php,如下:
<?php /** * 字体大小装饰器 */ namespace Think; class sizeDecorator implements decorator{ protected $size; public function __construct($size) { $this->size = $size; } public function beforeDraw() { echo "size decorator {$this->size}\n"; } public function afterDraw() { echo "end size decorator\n"; } }
还有被装饰者 Think/echoText.php,如下:
<?php /** * 被装饰者 */ namespace Think; class echoText { protected $decorator = array(); //存放装饰器 //装饰方法 public function index() { //调用装饰器前置操作 $this->before(); echo "你好,我是装饰器\n"; //执行装饰器后置操作 $this->after(); } public function addDecorator(Decorator $decorator) { $this->decorator[] = $decorator; } //执行装饰器前置操作 先进先出 public function before() { foreach ($this->decorator as $decorator){ $decorator->beforeDraw(); } } //执行装饰器后置操作 先进后出 public function after() { $decorators = array_reverse($this->decorator); foreach ($decorators as $decorator){ $decorator->afterDraw(); } } }
再来个自动加载 Think/Loder.php,如下:
<?php namespace Think; class Loder{ static function autoload($class){ require BASEDIR . '/' .str_replace('\\','/',$class) . '.php'; } }
最后就是入口文件index.php了,如下:
<?php define('BASEDIR',__DIR__); include BASEDIR . '/Think/Loder.php'; spl_autoload_register('\\Think\\Loder::autoload'); //实例化输出类 $echo = new \Think\echoText(); //增加装饰器 $echo->addDecorator(new \Think\colorDecorator('red')); //增加装饰器 $echo->addDecorator(new \Think\sizeDecorator('12')); //装饰方法 $echo->index();
咱最后再来一个案例啊,就是Web服务层 ―― 为 REST 服务提供 JSON 和 XML 装饰器,来看代码:
RendererInterface.php
<?php namespace DesignPatterns\Structural\Decorator; /** * RendererInterface接口 */ interface RendererInterface { /** * render data * * @return mixed */ public function renderData(); }
Webservice.php
<?php namespace DesignPatterns\Structural\Decorator; /** * Webservice类 */ 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
<?php namespace DesignPatterns\Structural\Decorator; /** * 装饰器必须实现 RendererInterface 接口, 这是装饰器模式的主要特点, * 否则的话就不是装饰器而只是个包裹类 */ /** * Decorator类 */ abstract class Decorator implements RendererInterface { /** * @var RendererInterface */ protected $wrapped; /** * 必须类型声明装饰组件以便在子类中可以调用renderData()方法 * * @param RendererInterface $wrappable */ public function __construct(RendererInterface $wrappable) { $this->wrapped = $wrappable; } }
RenderInXml.php
<?php namespace DesignPatterns\Structural\Decorator; /** * RenderInXml类 */ 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(); } }
RenderInJson.php
<?php namespace DesignPatterns\Structural\Decorator; /** * RenderInJson类 */ class RenderInJson extends Decorator { /** * render data as JSON * * @return mixed|string */ public function renderData() { $output = $this->wrapped->renderData(); return json_encode($output); } }
Tests/DecoratorTest.php
<?php namespace DesignPatterns\Structural\Decorator\Tests; use DesignPatterns\Structural\Decorator; /** * DecoratorTest 用于测试装饰器模式 */ 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 XML 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() { if (version_compare(PHP_VERSION, '7', '>=')) { throw new \PHPUnit_Framework_Error('Skip test for PHP 7', 0, __FILE__, __LINE__); } $this->getMockForAbstractClass('DesignPatterns\Structural\Decorator\Decorator', array(new \stdClass())); } /** * Second key-point of this pattern : the decorator is type-hinted * * @requires PHP 7 * @expectedException TypeError */ public function testDecoratorTypeHintedForPhp7() { $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); } }
好啦,本次记录就到这里了。
免责声明:本站发布的内容(图片、视频和文字)以原创、转载和分享为主,文章观点不代表本网站立场,如果涉及侵权请联系站长邮箱:mmqy2019@163.com进行举报,并提供相关证据,查实之后,将立刻删除涉嫌侵权内容。
长按识别二维码并关注微信
更方便到期提醒、手机管理