Question

I need a double pointer of type DizzyCreature (my class) to point to an array of DizzyCreature pointers. When I run it I get “Access violation reading location 0x…”. I can make a DizzyCreature* and call its member functions just fine, but when cannot run through the array and do the same thing for each obj.

I am following these instructions:
http://www.cplusplus.com/forum/beginner/10377/

Code

Server.h:

class Server
{
 public:
  Server(int x, int y, int count);
  ~Server(void);

  void tick();


 private:
  DizzyCreature** dcArrPtr;
  DizzyCreature* dcPtr;

  int _count;
};

Server.cpp:

Server::Server(int x, int y, int count)
{
  dcPtr = new DizzyCreature[count];       // this works just fine

  dcArrPtr = new DizzyCreature*[count];   // this doesn't (but gets past this line)
  _count = count;
}

Server::~Server(void)
{
  delete[] *dcArrPtr;
  delete[] dcPtr;
}

void Server::tick()
{
  dcPtr->takeTurn();                // just fine

  for (int i = 0; i < _count; i++) {
    dcArrPtr[i]->takeTurn();        // crash and burn
  }
}

EDIT:
The member function takeTurn() is in a parent class of DizzyCreature. The program makes it into the function, but as soon as it attempts to change a private member variable the exception is thrown. If it matters, DizzyCreature is of type GameCreature and WhirlyB as this is an assignment on MI.

Answer 1

You have allocated space for dcArrPtr, but didn’t allocate every object in this array. You must do following:

Server::Server(int x, int y, int count)
{
  dcPtr = new DizzyCreature[count];

  dcArrPtr = new DizzyCreature*[count];
  for ( int i = 0; i < count; i++ ) {
    dcArrPtr[ i ] = new DizzyCreature;
  }
  _count = count;
}

Server::~Server(void)
{
  for ( int i = 0; i < count; i++ ) {
    delete dcArrPtr[ i ];
  }
  delete[] *dcArrPtr;
  delete[] dcPtr;
}