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());