C++抽象基类的实例化（抽象工厂模式）

今天学习设计模式《抽象工厂模式》，参考了两个博客：

http://blog.csdn.net/wuzhekai1985/article/details/6660462

http://www.cnblogs.com/wanggary/archive/2011/04/13/2015288.html

然后按照第二个博客的意见，应用类模板实现工厂类；中间出现一个不能实例化抽象基类的问题，通过查资料，然后另外新建一个工程实验后知道：

1，抽象类是不能初始化的（最基本的，大家都知道的）

2，如果抽象基类的派生类有哪怕只有一个函数没有实现，这个抽象基类仍然不能实例化；即需要将抽象基类中定义的虚接口函数全部在派生类中实现（说的不太专业。。。）

代码如下：

//core.h#ifndef _CORE_H_#define _CORE_H_class Core{public:Core(){}virtual ~Core(){}virtual void NumOfCore() = 0;virtual void SpeedOfCore() = 0;virtual void VersionOfCore() = 0;};#endif

<pre name="code" class="cpp">//multicore.h#ifndef _MULTICORE_H_#define _MULTICORE_H_#include"core.h"#include<iostream>using namespace std;class MultiCore :public Core{public:MultiCore(){}~MultiCore(){}void NumOfCore(){cout << "multicore" << endl;}void SpeedOfCore(){cout << "speed fast" << endl;}virtual void VersionOfCore() = 0;};#endif

<pre name="code" class="cpp">//singlecore.h#ifndef _SINGLECORE_H_#define _SINGLECORE_H_#include"core.h"#include<iostream>using namespace std;class SingleCore :public Core{public:SingleCore(){}~SingleCore(){}void NumOfCore(){cout << "singlecore" << endl;}void SpeedOfCore(){cout << "speed slow" << endl;}virtual void VersionOfCore() = 0;};#endif

<pre name="code" class="cpp">//newmulticore.h#ifndef _NEWMULTICORE_H_#define _NEWMULTICORE_H_#include"multicore.h"class NewMultiCore :public MultiCore{public:NewMultiCore(){}~NewMultiCore(){}void VersionOfCore(){cout << "new multi version core" << endl;}};#endif

<pre name="code" class="cpp">//newsinglecore.h#ifndef _NEWSINGLECORE_H_#define _NEWSINGLECORE_H_#include"singlecore.h"class NewSingleCore :public SingleCore{public:NewSingleCore(){}~NewSingleCore(){}void VersionOfCore(){cout << "new single version core" << endl;}};#endif

<pre name="code" class="cpp">//oldmulticore.h#ifndef _OLDMULTICORE_H_#define _OLDMULTICORE_H_#include"multicore.h"class OldMultiCore :public MultiCore{public:OldMultiCore(){}~OldMultiCore(){}void VersionOfCore(){cout << "old multi version core" << endl;}};#endif

<pre name="code" class="cpp">//oldsinglecore.h#ifndef _OLDSINGLECORE_H_#define _OLDSINGLECORE_H_#include"singlecore.h"class OldSingleCore :public SingleCore{public:OldSingleCore(){}~OldSingleCore(){}void VersionOfCore(){cout << "old single version core" << endl;}};#endif

<pre name="code" class="cpp">//factory.h#ifndef _FACTORY_H_#define _FACTORY_H_#include"core.h"class Factory{public:Factory(){}virtual ~Factory(){}virtual Core* CreateSingleCore() = 0;virtual Core* CreateMultiCore() = 0;};#endif

<pre name="code" class="cpp">//newversionfactory.h#ifndef _NEWVERSIONFACTORY_H_#define _NEWVERSIONFACTORY_H_#include"factory.h"template<class T>class NewVersionFactory :public Factory{public:NewVersionFactory();~NewVersionFactory();Core* CreateMultiCore();Core* CreateSingleCore();};template<class T>NewVersionFactory<T>::NewVersionFactory(){}template<class T>NewVersionFactory<T>::~NewVersionFactory(){}template<class T>Core* NewVersionFactory<T>::CreateMultiCore(){return new T;}template<class T>Core* NewVersionFactory<T>::CreateSingleCore(){return new T;}#endif

//oldversionfactory.h#ifndef _OLDVERSIONFACTORY_H_#define _OLDVERSIONFACTORY_H_#include"factory.h"template<class T>class OldVersionFactory :public Factory{public:OldVersionFactory();~OldVersionFactory();Core* CreateMultiCore();Core* CreateSingleCore();};template<class T>OldVersionFactory<T>::OldVersionFactory(){}template<class T>OldVersionFactory<T>::~OldVersionFactory(){}template<class T>Core* OldVersionFactory<T>::CreateMultiCore(){return new T;}template<class T>Core* OldVersionFactory<T>::CreateSingleCore(){return new T;}#endif

//main.cpp#include"core.h"#include"factory.h"#include"multicore.h"#include"singlecore.h"#include"newversionfactory.h"#include"oldversionfactory.h"#include"newmulticore.h"#include"newsinglecore.h"#include"oldmulticore.h"#include"oldsinglecore.h"void main(){Factory* pFactoryMultiCore = new NewVersionFactory<NewMultiCore>();pFactoryMultiCore->CreateMultiCore()->NumOfCore();pFactoryMultiCore->CreateMultiCore()->SpeedOfCore();pFactoryMultiCore->CreateMultiCore()->VersionOfCore();delete pFactoryMultiCore;pFactoryMultiCore = NULL;Factory* pFactorySingleCore = new OldVersionFactory<OldSingleCore>();pFactorySingleCore->CreateSingleCore()->NumOfCore();pFactorySingleCore->CreateSingleCore()->SpeedOfCore();pFactorySingleCore->CreateSingleCore()->VersionOfCore();delete pFactorySingleCore;pFactorySingleCore = NULL;}