图形学优化_3: ogre设计模式_Singleton（单例模式）

http://blog.csdn.net/wuzhekai1985/article/details/6665869

• 由于构造函数是私有的，因此无法通过构造函数实例化，唯一的方法就是通过调用静态函数GetInstance

//Singleton.h  class Singleton    {  public:      static Singleton* GetInstance();  private:      Singleton() {}      static Singleton *singleton;  };  //Singleton.cpp  Singleton* Singleton::singleton = NULL;  Singleton* Singleton::GetInstance()  {      if(singleton == NULL)          singleton = new Singleton();      return singleton;  } 

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Singleton类的子类

//Singleton.h#pragma once#include <iostream>using namespace std;class Singleton  {public:    static Singleton* GetInstance(const char* name);    virtual void Show() {}protected: //必须为保护，如果是私有属性，子类无法访问父类的构造函数    Singleton() {}private:    static Singleton *singleton; //唯一实例的指针};//Singleton.cpp#include "Singleton.h"#include "SingletonA.h"#include "SingletonB.h"Singleton* Singleton::singleton = NULL;Singleton* Singleton::GetInstance(const char* name){    if(singleton == NULL)    {        if(strcmp(name, "SingletonA") == 0)            singleton = new SingletonA();        else if(strcmp(name,"SingletonB") == 0)            singleton = new SingletonB();        else             singleton = new Singleton();    }    return singleton;}

//SingletonA.h#pragma once#include "Singleton.h"class SingletonA: public Singleton{    friend class Singleton; //必须为友元类，否则父类无法访问子类的构造函数public:    void Show() { cout<<"SingletonA"<<endl; }private:   //为保护属性，这样外界无法通过构造函数进行实例化    SingletonA() {} };//SingletonB.h#pragma once#include "Singleton.h"class SingletonB: public Singleton{    friend class Singleton; //必须为友元类，否则父类无法访问子类的构造函数public:    void Show(){ cout<<"SingletonB"<<endl; }private:  //为保护属性，这样外界无法通过构造函数进行实例化    SingletonB() {}};

#include "Singleton.h"int main(){    Singleton *st = Singleton::GetInstance("SingletonA");    st->Show();    return 0;}

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多线程

• 多线程情况下加锁(lock)

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