PHP设计模式之：工厂模式

工厂模式：
由工厂类根据参数来决定创建出哪一种产品类的实例；
工厂类是指包含了一个专门用来创建其他对象的方法的类。所谓按需分配，传入参数进行选择，返回具体的类。工厂模式的最主要作用就是对象创建的封装、简化创建对象操作。 
简单的说，就是调用工厂类的一个方法（传入参数）来得到需要的类；

代码实现：

示例1（最基本的工厂类）：<?php class MyObject { public function __construct(){} public function test(){return '测试';} } class MyFactory { public static function factory(){//返回对象的实例return new MyObject();} } //调用工厂类MyFactory中的静态方法,获取类MyObject的实例$myobject=MyFactory::factory();echo $myobject->test(); 示例2：<?php//简单工厂模式/1* * 定义运算类 */abstract class Operation { protected $_NumberA = 0;protected $_NumberB = 0;protected $_Result  = 0; public function __construct($A,$B){$this->_NumberA = $A;$this->_NumberB = $B;} public function setNumber($A,$B){$this->_NumberA = $A;$this->_NumberB = $B;} /1*protected function clearResult(){$this->_Result  = 0;}*/ public function clearResult(){$this->_Result  = 0;} //抽象方法无方法体abstract protected function getResult(); } //继承一个抽象类的时候，子类必须实现抽象类中的所有抽象方法；//另外，这些方法的可见性 必须和抽象类中一样（或者更为宽松）class OperationAdd extends Operation { public function getResult(){$this->_Result=$this->_NumberA + $this->_NumberB;return $this->_Result;} } class OperationSub extends Operation { public function getResult(){$this->_Result=$this->_NumberA - $this->_NumberB;return $this->_Result;} } class OperationMul extends Operation { public function getResult(){$this->_Result=$this->_NumberA * $this->_NumberB;return $this->_Result;} } class OperationDiv extends Operation { public function getResult(){$this->_Result=$this->_NumberA / $this->_NumberB;return $this->_Result;} } class OperationFactory { //创建保存实例的静态成员变量private static $obj; //创建访问实例的公共的静态方法public static function CreateOperation($type,$A,$B){switch($type){case '+':self::$obj = new OperationAdd($A,$B);break;case '-':self::$obj = new OperationSub($A,$B);break;case '*':self::$obj = new OperationMul($A,$B);break;case '/':self::$obj = new OperationDiv($A,$B);break;}return self::$obj;} } //$obj = OperationFactory::CreateOperation('+');//$obj->setNumber(4,4);$obj = OperationFactory::CreateOperation('*',5,6);echo $obj->getResult();/1*echo '<br>';$obj->clearResult();echo '<br>';echo $obj->_Result;*/ 示例3：<?php//抽象工厂 //青铜会员的打折商品class BronzeRebateCommodity {//描述public $desc = '青铜会员的打折商品';} //白银会员的打折商品class SilverRebateCommodity {public $desc = '白银会员的打折商品';} //青铜会员的推荐商品class BronzeCommendatoryCommodity {public $desc = '青铜会员的推荐商品';} //白银会员的推荐商品class SilverCommendatoryCommodity {public $desc = '白银会员的推荐商品';} //各个工厂的接口interface ConcreteFactory {//生产对象的方法public function create($what);} //青铜工厂class BronzeFactory implements ConcreteFactory { //生产对象的方法public function create($what){$productName = 'Bronze'.$what.'Commodity';return new $productName;} } //白银工厂class SilverFactory implements ConcreteFactory { //生产对象的方法public function create($what){$productName = 'Silver'.$what.'Commodity';return new $productName;} } //调度中心class CenterFactory { //获取工厂的方法public function getFactory($what){$factoryName = $what.'Factory';return new $factoryName;} //获取工厂的静态方法public static function getFactory2($what){$factoryName = $what.'Factory';return new $factoryName;} } //实例化调度中心$center  = new CenterFactory();//获得一个白银工厂$factory = $center->getFactory('Silver');//让白银工厂制造一个推荐商品$product = $factory->create('Commendatory');//得到白银会员的推荐商品echo $product->desc.'<br>'; //获得一个青铜工厂$factory2 = CenterFactory::getFactory2('Bronze');//让青铜工厂制造一个打折商品$product2 = $factory2->create('Rebate');//得到青铜会员的推荐商品echo $product2->desc; 示例4：<?php//使用工厂类解析图像文件interface IImage { function getWidth();function getHeight();function getData(); } class Image_PNG implements IImage { protected $_width,$_height,$_data; public function __construct($file){$this->_file = $file;$this->_parse();} private function _parse(){//完成PNG格式的解析工作//并填充$_width,$_height和$_data$this->_data   = getimagesize($this->_file);list($this->_width,$this->_height)=$this->_data;} public function getWidth(){return $this->_width;} public function getHeight(){return $this->_height;} public function getData(){return $this->_data;} } class Image_JPEG implements IImage { protected $_width,$_height,$_data; public function __construct($file){$this->_file = $file;$this->_parse();} private function _parse(){//完成JPEG格式的解析工作//并填充$_width,$_height和$_data//$this->_width  = imagesx($this->_file);//$this->_height = imagesy($this->_file);$this->_data   = getimagesize($this->_file);list($this->_width,$this->_height)=$this->_data;} public function getWidth(){return $this->_width;} public function getHeight(){return $this->_height;} public function getData(){return $this->_data;} } //工厂类class ImageFactory { public static function factory($file){ $filename = pathinfo($file);switch(strtolower($filename['extension'])){case 'jpg':$return = new Image_JPEG($file);break;case 'png':$return = new Image_PNG($file);break;default:echo '图片类型不正确';break;}if($return instanceof IImage){return $return;}else{echo '出错了';exit();} } } $image = ImageFactory::factory('images/11.jpg');var_dump($image->getWidth());echo '<br>';print_r($image->getheight());echo '<br>';print_r($image->getData());