1、模式定义

简单工厂的作用是 实例化 对象，而不需要客户了解这个对象属于哪个具体的子类。简单工厂实例化的类具有相同的接口或者基类，在子类比较固定并不需要扩展时，可以使用简单工厂。

2、UML类图

3、实例代码

ConcreteFactory.php

<?php
namespace DesignPatterns\Creational\SimpleFactory;
/**
 * ConcreteFactory类
 */
class ConcreteFactory
{
 /**
 * @var array
 */
  protected  $ type List;
 /**
 * 你可以在这里注入自己的车子类型
 */
 public function __construct()
 {
 $this->typeList = array(
 'bicycle' => __NAMESPACE__ . '\Bicycle',
 'other' => __NAMESPACE__ . '\Scooter'
 );
 }
 /**
 * 创建车子
 *
 * @param string $type a known type key
 *
 * @return VehicleInterface a new instance of VehicleInterface
 * @ throws  \InvalidArgumentException
 */
 public function createVehicle($type)
 {
 if (!array_key_exists($type, $this->typeList)) {
 throw new \InvalidArgumentException("$type is not valid vehicle");
 }
 $className = $this->typeList[$type];
 return new $className();
 }
}
 

VehicleInterface.php

<?php
namespace DesignPatterns\Creational\SimpleFactory;
/**
 * VehicleInterface 是车子接口
 */
interface VehicleInterface
{
 /**
 * @param mixed $destination
 *
 * @return mixed
 */
 public function driveTo($destination);
}
 

Bicycle.php

<?php
namespace DesignPatterns\Creational\SimpleFactory;
/**
 * 自行车类
 */
class Bicycle implements VehicleInterface
{
 /**
 * @param mixed $destination
 *
 * @return mixed| void 
 */
 public function driveTo($destination)
 {
 }
}
 

Scooter.php

<?php
namespace DesignPatterns\Creational\SimpleFactory;
/**
 * 摩托车类
 */
class Scooter implements VehicleInterface
{
 /**
 * @param mixed $destination
 */
 public function driveTo($destination)
 {
 }
}
 

4、测试代码

Tests/SimpleFactoryTest.php

<?php
namespace DesignPatterns\Creational\SimpleFactory\Tests;
use DesignPatterns\Creational\SimpleFactory\ConcreteFactory;
/**
 * SimpleFactoryTest 用于测试 简单工厂模式 
 */
class SimpleFactoryTest extends \PHPUnit_Framework_TestCase
{
 protected $factory;
 protected function setUp()
 {
 $this->factory = new ConcreteFactory();
 }
 public function getType()
 {
 return array(
 array('bicycle'),
 array('other')
 );
 }
 /**
 * @dataProvider getType
 */
 public function testCreation($type)
 {
 $obj = $this->factory->createVehicle($type);
 $this->assertInstanceOf('DesignPatterns\Creational\SimpleFactory\VehicleInterface', $obj);
 }
 /**
 * @expectedException \InvalidArgumentException
 */
 public function testBadType()
 {
 $this->factory->createVehicle('car');
 }
}
 

5、总结

采用简单工厂的优点是可以使用户根据参数获得对应的类实例，避免了直接实例化类，降低了耦合性；缺点是可实例化的类型在编译期间已经被确定，如果增加新类型，则需要修改工厂，不符合OCP（开闭原则）的原则。简单工厂需要知道所有要生成的类型，当子类过多或者子类层次过多时不适合使用。