C++ class forward declaration

Question

When I try to compile this code i get:

52 C:\\Dev-Cpp\\Projektyyy\\strategy\\Tiles.h invalid use of undefined type `struct tile_tree_apple\' 
46 C:\\Dev-Cpp\         


        

Answer 1

To do anything other than declare a pointer to an object, you need the full definition.

The best solution is to move the implementation in a separate file.

If you must keep this in a header, move the definition after both declarations:

class tile_tree_apple;

class tile_tree : public tile
{
  public:
      tile onDestroy();
      tile tick();
      void onCreate();        
};

class tile_tree_apple : public tile
{
  public:
      tile onDestroy();
      tile tick();
      void onCreate(); 
      tile onUse();       
};

tile tile_tree::onDestroy() {return *new tile_grass;};
tile tile_tree::tick() {if (rand()%20==0) return *new tile_tree_apple;};
void tile_tree::onCreate() {health=rand()%5+4; type=TILET_TREE;};        

tile tile_tree_apple::onDestroy() {return *new tile_grass;};
tile tile_tree_apple::tick() {if (rand()%20==0) return *new tile_tree;};
void tile_tree_apple::onCreate() {health=rand()%5+4; type=TILET_TREE_APPLE;}; 
tile tile_tree_apple::onUse() {return *new tile_tree;};       

Important

You have memory leaks:

tile tile_tree::onDestroy() {return *new tile_grass;};

will create an object on the heap, which you can't destroy afterwards, unless you do some ugly hacking. Also, your object will be sliced. Don't do this, return a pointer.