Question

I’m making a class that adds some basic operations to an std::map, and I would like to automatically call delete after removing an item from the map. But if the second (T2) value isn’t a pointer, this can’t be done. Is there any way to check?

template <class T,class T2>
bool CExtendedMap<T,T2>::remove(T ID)
{
    if(theMap.find(ID)!=theMap.end())
    {
        T2 second = theMap.find(ID)->second;
        theMap.erase(theMap.find(ID));
        //delete second; //Had to comment it out now.
        return true;
    }
    return false;
}

Answer 1

If I understand your question correctly you’d like to behave differently if the value of the paired stored in your CExtendedMap is or isn’t a pointer.

One easy way of solving the issue is to use template overloads to get the desired effect.

Implement a wrapper function that will use delete if the parameter is a pointer, or do nothing if it’s not, that’s by far the easiest solution.

A sample implementation is provided below:

template<class T> inline
void delete_or_nop (T  const&)    {/* NOP */}

template<class T> inline
void delete_or_nop (T* const& p)  {delete p;}

---

int
main (int argc, char *argv[])
{
  int * p = 0;
  int   n = 0;

  delete_or_nop (p);
  delete_or_nop (n);
}