设计模式（简单工厂模式）

　　建立对象的类就如一个工厂，而需要被建立的对象就如一个个产品。

#include <iostream>
#include <vector>
using namespace std;

typedef enum ProductTypeTag
{
	TypeA,
	TypeB,
	TypeC
}PRODUCTTYPE;

// Here is the product class
class Product
{
public:
	virtual void Show() = 0;
};

class ProductA : public Product
{
public:
	void Show()
	{
		cout<<"I‘m ProductA"<<endl;
	}
};

class ProductB : public Product
{
public:
	void Show()
	{
		cout<<"I‘m ProductB"<<endl;
	}
};

class ProductC : public Product
{
public:
	void Show()
	{
		cout<<"I‘m ProductC"<<endl;
	}
};

// Here is the Factory class
class Factory
{
public:
	Product* CreateProduct(PRODUCTTYPE type)
	{
		switch (type)
		{
		case TypeA:
			return new ProductA();

		case TypeB:
			return new ProductB();

		case TypeC:
			return new ProductC();

		default:
			return NULL;
		}
	}
};

int main(int argc, char *argv[])
{
	// First, create a factory object
	Factory *ProductFactory = new Factory();
	Product *productObjA = ProductFactory->CreateProduct(TypeA);
	if (productObjA != NULL)
		productObjA->Show();

	Product *productObjB = ProductFactory->CreateProduct(TypeB);
	if (productObjB != NULL)
		productObjB->Show();

	Product *productObjC = ProductFactory->CreateProduct(TypeC);
	if (productObjC != NULL)
		productObjC->Show();

	delete ProductFactory;
	ProductFactory = NULL;

	delete productObjA;
	productObjA = NULL;

	delete productObjB;
	productObjB = NULL;        

	delete productObjC;
	productObjC = NULL;

	return 0;
}