C++ Code Example: Singleton Class (Ex:4)

Sphere: Related Content #include <iostream>
using namespace std;

class Singleton
{
  public:
    static Singleton* Instance();
  protected:
   Singleton();
    //Singleton(const Singleton&);
    //Singleton& operator= (const Singleton&);
  private:
    static Singleton* pinstance;
};
Singleton* Singleton::pinstance = 0;// initialize pointer

Singleton* Singleton::Instance ()
{
  if (pinstance == 0) // is it the first call?
  {
      pinstance = new Singleton; // create sole instance
  }
return pinstance; // address of sole instance
}
Singleton::Singleton()
{
    //... perform necessary instance initializations
    cout << "Calling Protected Constructor" << endl;
}

int main()
{
    Singleton *p1 = Singleton::Instance();
    Singleton *p2 = p1->Instance();
    Singleton & ref = * Singleton::Instance();

    return 0;
}