SingleTon Pattern

 1 #ifndef _SINGLETON_H_
 2 #define _SINGLETON_H_
 3 
 4 #include <iostream>
 5 using namespace std;
 6 
 7 class Singleton
 8 {
 9  public:
10     static Singleton* Instance();
11 
12  protected:
13     Singleton();
14 
15  private:
16     static Singleton* _instance;
17 }
18 
19 #endif

Singleton.h

 1 #include "Singleton.h"
 2 
 3 #include <iostream>
 4 using namespace std;
 5 
 6 Singleton* Singleton::_instance = 0;
 7 Singleton::Singleton()
 8 {
 9   cout<<"Singleton...."<<endl;
10 }
11 
12 Singleton* Singleton::Instance()
13 {
14   if(_instance == 0)
15        _instance = new Singleton();  
16   
17   return _instance;  
18 }

Singleton.cpp

注：Singleton不可以被实例化，因此将其构造函数声明为protected或者直接声明为private。