CPP/Classes/Singleton

Singleton.cpp

#include <iostream>
 
class Log
{
  public:
    static Log* Instance()
    {
      if (!instance)   // Only allow one instance of class to be generated.
        {
        instance = new Log;
        }
 
      return instance;
 
    }
 
    double val;
 
  private:
    Log(){}
    Log& operator=(const Log&); //prevent assignment
    Log(const Log&);//prevent copy construction
 
    static Log* instance; //store the single instance
 
};
 
Log* Log::instance = NULL; 
 
int main(int argc, char* argv[])
{
  Log::Instance()->val = 2.0;
 
  std::cout << "val = " << Log::Instance()->val << std::endl;;
 
	return 0;
}