作用:
定義一個用于創建對象的接口，讓子類決定實例化哪一個類。Factory Method 使一個類的實例化延遲到其子類。
UML結構圖:
抽象基類:
1)Product:創建出來的對象的抽象基類.
2)Factory創建對象的工廠方法的抽象基類.
接口函數:
1)Creator::FactoryMethod:純虛函數,由派生類實現,創建出對應的Product.
解析:
在這個模式中,有兩個抽象基類,一個是Product為創建出來的對象的抽象基類,一個是Factory是工廠的抽象基類,在互相協作的時候都是由相應的Factory派生類來生成Product的派生類,也就是說如果要新增一種Product那么也要對應的新增一個Factory,創建的過程委托給了這個Factory.也就是說一個Factory和一個Product是一一對應的關系.
備注:
設計模式的演示圖上把Factory類命名為Creator,下面的實現沿用了這個命名.
演示實現:
1)Factory.h
/**//********************************************************************
????created:????2006/06/30
????filename:?????Factory.h
????author:????????李創
????????????????http://www.shnenglu.com/converse/
????purpose:????Factory模式的演示代碼
*********************************************************************/
#ifndef?FACTORY_H
#define?FACTORY_H
class?Product
{
public:
????Product(){}
????virtual?~Product(){}
};
class?ConcreateProduct
????:?public?Product
{
public:
????ConcreateProduct();
????virtual?~ConcreateProduct();
};
class?Creator
{
public:
????Creator(){}
????virtual?~Creator(){}
????void?AnOperation();
protected:
????virtual?Product*?FactoryMethod()?=?0;
};
class?ConcreateCreator
????:?public?Creator
{
public:
????ConcreateCreator();
????virtual?~ConcreateCreator();
protected:
????virtual?Product*?FactoryMethod();
};
#endif
2)Factory.cpp
/**//********************************************************************
????created:????2006/06/30
????filename:?????Factory.cpp
????author:????????李創
????????????????http://www.shnenglu.com/converse/
????purpose:????Factory模式的演示代碼
*********************************************************************/
#include?"Factory.h"
#include?<iostream>
using?namespace?std;
ConcreateProduct::ConcreateProduct()
{
????std::cout?<<?"construction?of?ConcreateProduct\n";
}
ConcreateProduct::~ConcreateProduct()
{
????std::cout?<<?"destruction?of?ConcreateProduct\n";
}
void?Creator::AnOperation()
{
????Product*?p?=?FactoryMethod();
????std::cout?<<?"an?operation?of?product\n";
}
ConcreateCreator::ConcreateCreator()
{
????std::cout?<<?"construction?of?ConcreateCreator\n";
}
ConcreateCreator::~ConcreateCreator()
{
????std::cout?<<?"destruction?of?ConcreateCreator\n";
}
Product*?ConcreateCreator::FactoryMethod()
{
????return?new?ConcreateProduct();
}
3)Main.cpp(測試代碼)
/**//********************************************************************
????created:????2006/06/30
????filename:?????Main.cpp
????author:????????李創
????????????????http://www.shnenglu.com/converse/
????purpose:????測試Factory模式的代碼
*********************************************************************/
#include?"Factory.h"
#include?<stdlib.h>
int?main(int?argc,char*?argv[])
{
????Creator?*p?=?new?ConcreateCreator();
????p->AnOperation();
????delete?p;
????system("pause");
????return?0;
}