creating one object

[dorA26]

Hey guys,
I need to create a class, from which only one object can be created, and if there's an attempt to create another object of this class it gets the address of the first object (they'll both point at the same object..)
Can anyone help? thanks a lot!

[johnbob]

http://en.wikipedia.org/wiki/Singleton_pattern

[vlad from moscow]

One of possible approaches

#include <cassert>

class Singleton
{
public:
   static Singleton * create()
   {
      static Singleton obj;
      return &obj;
   }
private:
   Singleton() {}
};


int main()
{
   Singleton *obj1 = Singleton::create();
   Singleton *obj2 = Singleton::create();

   assert( obj1 == obj2 );
} 

Another way is to have a static member that will keep how many objects are created and to have another static object that will keep address of the first created object. Something as

class Singleton
{
public:
   static Singleton *create()
   {
      if ( count == 0 )
      {
         obj = new Singleton();
      }

      return ( obj );
   }
private:
   Singleton() { count = 1; }
   ~Singleton() { delete obj; obj = 0; count = 0; }
   static size_t count;
   static Singleton *obj;
};

[dorA26]

thanks!