100分要个求单例实现的代码 求一个设计模式中单例的例子 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 #include <iostream>using namespace std;//单例类的C++实现class Singleton{private:Singleton();//注意:构造方法私有virtual ~Singleton();static Singleton* instance;//惟一实例int var;//成员变量(用于测试)public:static Singleton* GetInstance();//工厂方法(用来获得实例)int getVar();//获得var的值void setVar(int);//设置var的值};//构造方法实现Singleton::Singleton(){this->var = 20;cout<<"Singleton Constructor"<<endl;}Singleton::~Singleton(){delete instance;}//初始化静态成员Singleton* Singleton::instance=new Singleton();Singleton* Singleton::GetInstance(){return instance;}//seter && getter含数int Singleton::getVar(){return this->var;}void Singleton::setVar(int var){this->var = var;}//mainint main(int argc, char* argv[]){Singleton *ton1 = Singleton::GetInstance();Singleton *ton2 = Singleton::GetInstance();cout<<"ton1 var = "<<ton1->getVar()<<endl;ton1->setVar(150);cout<<"ton2 var = "<<ton2->getVar()<<endl;return 0;} /*设计模式例程根据有关例程综合而成*//*意图: 提供一个创建一系列相关或相互依赖对象的接口,而无需指定它们具体的类。 适用性: 一个系统要独立于它的产品的创建、组合和表示时。 一个系统要由多个产品系列中的一个来配置时。 当你要强调一系列相关的产品对象的设计以便进行联合使用时。 当你提供一个产品类库,而只想显示它们的接口而不是实现时。 *//*MazeFactory <--------------------------------MazeGame ----> Maze | MapSite<----| BombedMazefactory | | EnchantedMazeFactory Door<---| MazePrototypeFactory Wall<---| Room<---|*//**/#include <iostream.h>#include "../public/MazeParts.H"#include "../public/MazeGame.H"#define MazeFactory_H/**/class MazeFactory {public: MazeFactory();/* { output("MazeFactory::MazeFactory()\n"); }; *//**/ virtual Maze* MakeMaze() const;// { return new Maze; } virtual Wall* MakeWall() const;// { return new Wall; } virtual Room* MakeRoom(int n) const;// { return new Room(n); } virtual Door* MakeDoor(Room* r1, Room* r2) const;// { return new Door(r1, r2); }};/**//* already maze.cppMaze* MazeGame::CreateMaze (MazeFactory& factory) { output("Maze* MazeGame::CreateMaze (MazeFactory& factory) \n"); Maze* aMaze = factory.MakeMaze(); Room* r1 = factory.MakeRoom(1); Room* r2 = factory.MakeRoom(2); Door* aDoor = factory.MakeDoor(r1, r2); aMaze->AddRoom(r1); aMaze->AddRoom(r2); r1->SetSide(North, factory.MakeWall()); r1->SetSide(East, aDoor); r1->SetSide(South, factory.MakeWall()); r1->SetSide(West, factory.MakeWall()); r2->SetSide(North, factory.MakeWall()); r2->SetSide(East, factory.MakeWall()); r2->SetSide(South, factory.MakeWall()); r2->SetSide(West, aDoor); return aMaze;}*//**/class EnchantedMazeFactory : public MazeFactory {public: EnchantedMazeFactory();/**/ virtual Room* MakeRoom(int n) const{ output("virtual Room* MakeRoom(int n) const\n"); return new EnchantedRoom(n, CastSpell()); }/**/ virtual Door* MakeDoor(Room* r1, Room* r2) const{ output(" virtual Door* MakeDoor(Room* r1, Room* r2) const\n"); return new DoorNeedingSpell(r1, r2); }/**/protected: Spell* CastSpell() const;};/**/#define EnchantedMazeFactory_H#include "../public/MazeFactories.H"/**//* already define maze.cppWall* BombedMazeFactory::MakeWall () const { output("Wall* BombedMazeFactory::MakeWall () const \n"); return new BombedWall;}*//**//*Room* BombedMazeFactory::MakeRoom(int n) const { output("Room* BombedMazeFactory::MakeRoom(int n) const {\n"); return new RoomWithABomb(n);}*//**/void main() { /* */ MazeGame game; BombedMazeFactory factory; game.CreateMaze(factory); /* */ pause();}//*** the end 刚才的是abstract factory现在是singletonSingleton模式是常用的设计模式之一,但是要实现一个真正实用的设计模式却也不是件容易的事情。1. 标准的实现class Singleton { public: static Singleton * Instance() { if( 0== _instance) { _instance = new Singleton; } return _instance; } protected: Singleton(void) { } virtual ~Singleton(void) { } static Singleton* _instance; }; 这是教科书上使用的方法。看起来没有什么问题,其实包含很多的问题。下面我们一个一个的解决。2. 自动垃圾回收上面的程序必须记住在程序结束的时候,释放内存。为了让它自动的释放内存,我们引入auto_ptr改变它。#include <memory> #include <iostream> using namespace std; class Singleton { public: static Singleton * Instance() { if( 0== _instance.get()) { _instance.reset( new Singleton); } return _instance.get(); } protected: Singleton(void) { cout <<"Create Singleton"<<endl; } virtual ~Singleton(void) { cout << "Destroy Singleton"<<endl; } friend class auto_ptr<Singleton>; static auto_ptr<Singleton> _instance; }; //Singleton.cppauto_ptr<Singleton> Singleton::_instance; 3. 增加模板在我的一个工程中,有多个的Singleton类,对Singleton类,我都要实现上面这一切,这让我觉得烦死了。于是我想到了模板来完成这些重复的工作。现在我们要添加本文中最吸引人单件实现:/******************************************************************** (c) 2003-2005 C2217 Studio Module: Singleton.h Created: 9/3/2005 23:17 Purpose: Implement singleton pattern History: *********************************************************************/ #pragma once #include <memory> using namespace std; using namespace C2217::Win32; namespace C2217 { namespace Pattern { template <class T> class Singleton { public: static inline T* instance(); private: Singleton(void){} ~Singleton(void){} Singleton(const Singleton&){} Singleton & operator= (const Singleton &){} static auto_ptr<T> _instance; }; template <class T> auto_ptr<T> Singleton<T>::_instance; template <class T> inline T* Singleton<T>::instance() { if( 0== _instance.get()) { _instance.reset ( new T); } return _instance.get(); } //Class that will implement the singleton mode, //must use the macro in it's delare file #define DECLARE_SINGLETON_CLASS( type ) \ friend class auto_ptr< type >;\ friend class Singleton< type >; } } 4. 线程安全上面的程序可以适应单线程的程序。但是如果把它用到多线程的程序就会发生问题。主要的问题在于同时执行_instance.reset ( new T); 就会同时产生两个新的对象,然后马上释放一个,这跟Singleton模式的本意不符。所以,你需要更加安全的版本: /******************************************************************** (c) 2003-2005 C2217 Studio Module: Singleton.h Author: Yangjun D. Created: 9/3/2005 23:17 Purpose: Implement singleton pattern History: *********************************************************************/ #pragma once #include <memory> using namespace std; #include "Interlocked.h" using namespace C2217::Win32; namespace C2217 { namespace Pattern{ template <class T> class Singleton { public: static inline T* instance(); private: Singleton(void){} ~Singleton(void){} Singleton(const Singleton&){} Singleton & operator= (const Singleton &){} static auto_ptr<T> _instance; static CResGuard _rs; }; template <class T> auto_ptr<T> Singleton<T>::_instance; template <class T> CResGuard Singleton<T>::_rs; template <class T> inline T* Singleton<T>::instance() { if( 0 == _instance.get() ) { CResGuard::CGuard gd(_rs); if( 0== _instance.get()) { _instance.reset ( new T); } } return _instance.get();} //Class that will implement the singleton mode, //must use the macro in it's delare file #define DECLARE_SINGLETON_CLASS( type ) \ friend class auto_ptr< type >;\ friend class Singleton< type >; } } CresGuard 类主要的功能是线程访问同步,代码如下: /****************************************************************************** Module: Interlocked.h Notices: Copyright (c) 2000 Jeffrey Richter ******************************************************************************/ #pragma once /////////////////////////////////////////////////////////////////////////////// // Instances of this class will be accessed by multiple threads. So, // all members of this class (except the constructor and destructor) // must be thread-safe. class CResGuard { public: CResGuard() { m_lGrdCnt = 0; InitializeCriticalSection(&m_cs); } ~CResGuard() { DeleteCriticalSection(&m_cs); } // IsGuarded is used for debugging BOOL IsGuarded() const { return(m_lGrdCnt > 0); } public: class CGuard { public: CGuard(CResGuard& rg) : m_rg(rg) { m_rg.Guard(); }; ~CGuard() { m_rg.Unguard(); } private: CResGuard& m_rg; }; private: void Guard() { EnterCriticalSection(&m_cs); m_lGrdCnt++; } void Unguard() { m_lGrdCnt--; LeaveCriticalSection(&m_cs); } // Guard/Unguard can only be accessed by the nested CGuard class. friend class CResGuard::CGuard; private: CRITICAL_SECTION m_cs; long m_lGrdCnt; // # of EnterCriticalSection calls };/////////////////////////////////////////////////////////////////////////////// 5. 实用方法比如你有一个需要实现单件模式的类,就应该这样实现:#pragma once #include "singleton.h" using namespace C2217::Pattern; class ServiceManger { public: void Run() { } private: ServiceManger(void) { } virtual ~ServiceManger(void) { } DECLARE_SINGLETON_CLASS(ServiceManger); }; typedef Singleton<ServiceManger> SSManger; 在使用的时候很简单,跟一般的Singleton实现的方法没有什么不同。int _tmain(int argc, _TCHAR* argv[]) { SSManger::instance()->Run(); } 一个简单的Singleton模式的实现,可以看到C++语言背后隐藏的丰富的语意,我希望有人能实现一个更好的Singleton让大家学习。我从一开始实现Singleton类的过程,其实就是我学习C++的过程,越是深入越觉得C++了不起。 using namespace std; class Single { private: static Single * p; public: static Single* getInstance(); }; Single * Single::p=0; Single* Single::getInstance() { if(p==0) p=new Single; return p; } 你们写的太麻烦了。class A{ public: static A* Instance() { static A a; return &a; }};用的地方这么用就好了。A* pA = A::Instance();pA->func(...); DirectShow在调用Stop的时候出错 IDispatch error #3092 ——SQL语法格式有问题? 有些时候,只知道DownloadComplete,怎么办呢? 将字符指针(char *)转换为字符串(String) 谁知道WDL文件的文件格式? ---100分问题,高手请指教--- 50 分求购IPHlpApi.lib和IPHlpApi.h文件! 0x00000002与2有什么差别 想学API怎么办?????????????????? 不用MFC如何通过ODBC编写数据库应用程序? OpengL动画问题 高手进来帮我看看这句话是什么意思???能用通俗一点的话来解释看看!
using namespace std;
//单例类的C++实现
class Singleton
{
private:
Singleton();//注意:构造方法私有
virtual ~Singleton();
static Singleton* instance;//惟一实例
int var;//成员变量(用于测试)
public:
static Singleton* GetInstance();//工厂方法(用来获得实例)
int getVar();//获得var的值
void setVar(int);//设置var的值
};
//构造方法实现
Singleton::Singleton()
{
this->var = 20;
cout<<"Singleton Constructor"<<endl;
}
Singleton::~Singleton()
{
delete instance;
}
//初始化静态成员
Singleton* Singleton::instance=new Singleton();
Singleton* Singleton::GetInstance()
{
return instance;
}
//seter && getter含数
int Singleton::getVar()
{
return this->var;
}
void Singleton::setVar(int var)
{
this->var = var;
}
//main
int main(int argc, char* argv[])
{
Singleton *ton1 = Singleton::GetInstance();
Singleton *ton2 = Singleton::GetInstance();
cout<<"ton1 var = "<<ton1->getVar()<<endl;
ton1->setVar(150);
cout<<"ton2 var = "<<ton2->getVar()<<endl;
return 0;
}
设计模式例程
根据有关例程综合而成
*/
/*
意图:
提供一个创建一系列相关或相互依赖对象的接口,而无需指定它们具体的类。
适用性:
一个系统要独立于它的产品的创建、组合和表示时。
一个系统要由多个产品系列中的一个来配置时。
当你要强调一系列相关的产品对象的设计以便进行联合使用时。
当你提供一个产品类库,而只想显示它们的接口而不是实现时。
*//*
MazeFactory <--------------------------------MazeGame ----> Maze
| MapSite<----|
BombedMazefactory | |
EnchantedMazeFactory Door<---|
MazePrototypeFactory Wall<---|
Room<---|
*//*
*/
#include <iostream.h>
#include "../public/MazeParts.H"
#include "../public/MazeGame.H"
#define MazeFactory_H/*
*/
class MazeFactory {
public:
MazeFactory();
/* {
output("MazeFactory::MazeFactory()\n");
};
*/
/*
*/
virtual Maze* MakeMaze() const;
// { return new Maze; }
virtual Wall* MakeWall() const;
// { return new Wall; }
virtual Room* MakeRoom(int n) const;
// { return new Room(n); }
virtual Door* MakeDoor(Room* r1, Room* r2) const;
// { return new Door(r1, r2); }
};
/*
*/
/* already maze.cppMaze* MazeGame::CreateMaze (MazeFactory& factory) {
output("Maze* MazeGame::CreateMaze (MazeFactory& factory) \n");
Maze* aMaze = factory.MakeMaze();
Room* r1 = factory.MakeRoom(1);
Room* r2 = factory.MakeRoom(2);
Door* aDoor = factory.MakeDoor(r1, r2); aMaze->AddRoom(r1);
aMaze->AddRoom(r2); r1->SetSide(North, factory.MakeWall());
r1->SetSide(East, aDoor);
r1->SetSide(South, factory.MakeWall());
r1->SetSide(West, factory.MakeWall()); r2->SetSide(North, factory.MakeWall());
r2->SetSide(East, factory.MakeWall());
r2->SetSide(South, factory.MakeWall());
r2->SetSide(West, aDoor); return aMaze;
}
*//*
*/
class EnchantedMazeFactory : public MazeFactory {
public:
EnchantedMazeFactory();
/*
*/
virtual Room* MakeRoom(int n) const{
output("virtual Room* MakeRoom(int n) const\n");
return new EnchantedRoom(n, CastSpell());
}
/*
*/
virtual Door* MakeDoor(Room* r1, Room* r2) const{
output(" virtual Door* MakeDoor(Room* r1, Room* r2) const\n");
return new DoorNeedingSpell(r1, r2);
}
/*
*/
protected:
Spell* CastSpell() const;
};
/*
*/
#define EnchantedMazeFactory_H
#include "../public/MazeFactories.H"
/*
*/
/* already define maze.cpp
Wall* BombedMazeFactory::MakeWall () const {
output("Wall* BombedMazeFactory::MakeWall () const \n");
return new BombedWall;
}
*/
/*
*/
/*
Room* BombedMazeFactory::MakeRoom(int n) const {
output("Room* BombedMazeFactory::MakeRoom(int n) const {\n");
return new RoomWithABomb(n);
}
*/
/*
*/
void main() {
/*
*/
MazeGame game;
BombedMazeFactory factory; game.CreateMaze(factory);
/*
*/
pause();
}//*** the end
现在是singleton
Singleton模式是常用的设计模式之一,但是要实现一个真正实用的设计模式却也不是件容易的事情。1. 标准的实现class Singleton
{
public:
static Singleton * Instance() {
if( 0== _instance)
{
_instance = new Singleton;
}
return _instance;
}
protected:
Singleton(void)
{
}
virtual ~Singleton(void)
{
}
static Singleton* _instance;
};
这是教科书上使用的方法。看起来没有什么问题,其实包含很多的问题。下面我们一个一个的解决。2. 自动垃圾回收上面的程序必须记住在程序结束的时候,释放内存。为了让它自动的释放内存,我们引入auto_ptr改变它。
#include <memory>
#include <iostream>
using namespace std;
class Singleton
{
public:
static Singleton * Instance()
{
if( 0== _instance.get())
{
_instance.reset( new Singleton);
}
return _instance.get();
}
protected:
Singleton(void)
{
cout <<"Create Singleton"<<endl;
}
virtual ~Singleton(void)
{
cout << "Destroy Singleton"<<endl;
}
friend class auto_ptr<Singleton>;
static auto_ptr<Singleton> _instance;
};
//Singleton.cpp
auto_ptr<Singleton> Singleton::_instance; 3. 增加模板在我的一个工程中,有多个的Singleton类,对Singleton类,我都要实现上面这一切,这让我觉得烦死了。于是我想到了模板来完成这些重复的工作。现在我们要添加本文中最吸引人单件实现:/********************************************************************
(c) 2003-2005 C2217 Studio
Module: Singleton.h
Created: 9/3/2005 23:17
Purpose: Implement singleton pattern
History:
*********************************************************************/
#pragma once
#include <memory>
using namespace std;
using namespace C2217::Win32;
namespace C2217
{
namespace Pattern
{
template <class T>
class Singleton
{
public:
static inline T* instance();
private:
Singleton(void){}
~Singleton(void){}
Singleton(const Singleton&){}
Singleton & operator= (const Singleton &){}
static auto_ptr<T> _instance;
};
template <class T>
auto_ptr<T> Singleton<T>::_instance;
template <class T>
inline T* Singleton<T>::instance()
{
if( 0== _instance.get())
{
_instance.reset ( new T);
}
return _instance.get();
}
//Class that will implement the singleton mode,
//must use the macro in it's delare file
#define DECLARE_SINGLETON_CLASS( type ) \
friend class auto_ptr< type >;\
friend class Singleton< type >;
}
}
4. 线程安全上面的程序可以适应单线程的程序。但是如果把它用到多线程的程序就会发生问题。主要的问题在于同时执行_instance.reset ( new T); 就会同时产生两个新的对象,然后马上释放一个,这跟Singleton模式的本意不符。所以,你需要更加安全的版本:
/********************************************************************
(c) 2003-2005 C2217 Studio
Module: Singleton.h
Author: Yangjun D.
Created: 9/3/2005 23:17
Purpose: Implement singleton pattern
History:
*********************************************************************/
#pragma once
#include <memory>
using namespace std;
#include "Interlocked.h"
using namespace C2217::Win32;
namespace C2217
{
namespace Pattern
{
template <class T>
class Singleton
{
public:
static inline T* instance();
private:
Singleton(void){}
~Singleton(void){}
Singleton(const Singleton&){}
Singleton & operator= (const Singleton &){}
static auto_ptr<T> _instance;
static CResGuard _rs;
};
template <class T>
auto_ptr<T> Singleton<T>::_instance;
template <class T>
CResGuard Singleton<T>::_rs;
template <class T>
inline T* Singleton<T>::instance()
{
if( 0 == _instance.get() )
{
CResGuard::CGuard gd(_rs);
if( 0== _instance.get())
{
_instance.reset ( new T);
}
}
return _instance.get();
}
//Class that will implement the singleton mode,
//must use the macro in it's delare file
#define DECLARE_SINGLETON_CLASS( type ) \
friend class auto_ptr< type >;\
friend class Singleton< type >;
}
}
CresGuard 类主要的功能是线程访问同步,代码如下:
/******************************************************************************
Module: Interlocked.h
Notices: Copyright (c) 2000 Jeffrey Richter
******************************************************************************/
#pragma once
///////////////////////////////////////////////////////////////////////////////
// Instances of this class will be accessed by multiple threads. So,
// all members of this class (except the constructor and destructor)
// must be thread-safe.
class CResGuard {
public:
CResGuard() { m_lGrdCnt = 0; InitializeCriticalSection(&m_cs); }
~CResGuard() { DeleteCriticalSection(&m_cs); }
// IsGuarded is used for debugging
BOOL IsGuarded() const { return(m_lGrdCnt > 0); }
public:
class CGuard {
public:
CGuard(CResGuard& rg) : m_rg(rg) { m_rg.Guard(); };
~CGuard() { m_rg.Unguard(); }
private:
CResGuard& m_rg;
};
private:
void Guard() { EnterCriticalSection(&m_cs); m_lGrdCnt++; }
void Unguard() { m_lGrdCnt--; LeaveCriticalSection(&m_cs); }
// Guard/Unguard can only be accessed by the nested CGuard class.
friend class CResGuard::CGuard;
private:
CRITICAL_SECTION m_cs;
long m_lGrdCnt; // # of EnterCriticalSection calls
};/////////////////////////////////////////////////////////////////////////////// 5. 实用方法比如你有一个需要实现单件模式的类,就应该这样实现:
#pragma once
#include "singleton.h"
using namespace C2217::Pattern;
class ServiceManger
{
public:
void Run()
{
}
private:
ServiceManger(void)
{
}
virtual ~ServiceManger(void)
{
}
DECLARE_SINGLETON_CLASS(ServiceManger);
};
typedef Singleton<ServiceManger> SSManger;
在使用的时候很简单,跟一般的Singleton实现的方法没有什么不同。
int _tmain(int argc, _TCHAR* argv[])
{
SSManger::instance()->Run();
}
一个简单的Singleton模式的实现,可以看到C++语言背后隐藏的丰富的语意,我希望有人能实现一个更好的Singleton让大家学习。我从一开始实现Singleton类的过程,其实就是我学习C++的过程,越是深入越觉得C++了不起。
class Single
{
private:
static Single * p;
public:
static Single* getInstance();
};
Single * Single::p=0;
Single* Single::getInstance()
{
if(p==0) p=new Single;
return p;
}
{
public:
static A* Instance()
{
static A a;
return &a;
}
};用的地方这么用就好了。A* pA = A::Instance();
pA->func(...);