Question

int buffer[gSizeOfGrid][gSizeOfGrid];
CList *currentCList;
Grid *currentGrid; //this line get the error
int aroundinfo[4];
//other functions are not revelant maybe? They don't
//use currentGrid.

the class Grid has the header:

class Grid
{
public:
    Grid();
    //create default cList object for the grid .
    Grid(CList*);
    //create cList and bind existing clist object.
    bool rebind(CList*);
    //rebind cList.
    ~Grid();
    void init(int ants,int bugs);
    //init a grid with ants and bugs according to parameter.
    void GetSnapshot();
    //synchronize grid buffer with clist.
    void Step();
    //make the world go on!
    bool spawn(Creature&,Position);
    //create a creature on the grid.
    //if success, return true.
    //if there are already another creature return false.
    void move(Position,int);
    void eat(Position,int);
    void breed(Position,int);
    void destroy(Position);
private:
    CList* theList;
};

the Clist Class looks the same but is Okay in declaration:

using namespace std;
class CList
{
public:
    CList();
    int CreateObject(Creature&,Position);
    Creature& GetObject(int);
    bool RemoveObject(Position);
    bool RemoveObject(int);
    int getType(Position);
    void cleanup();
    vector<Creature*> list;
    int size();
};

Why the Grid* declaration goes wrong but CList* is OK? Thank you!

Answer 1

This is because class Grid is not visible to the pointer currentGrid. Just do following and it should work;

class Grid;
Grid *currentGrid;

I assume that you may not want to #include the Grid header before this declaration as, Grid itself is using CList. The best way should be to include all the headers before this declarations.