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）：

  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

  //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：

  //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

  //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());