Programming Forums > Application Development > C++

ionexchange · Jan 4th, 2006, 10:30 PM

So I have this grid and it is made up of cells

class Cell{
private:
  int value;
public:
  void set_value(int in);
  int get_value(void);
  int  event_handler(void);
 // other code
};

This grid is made up row and columns which are the same type

(Toggle Plain Text)

class vec{
private:
  Cell* array[10];
public:
  void set_array(Cell* in);
  int  event_handler(void);
  //other code
};

class Grid{
private:
 vec[100];
public:
  void event_handler(void);
  // and other code
};

Vec contains and array of pointers to cell so I use vect to controll the behavior of the cell in vec. It is possible, howerver that the address (or controll of a cell) can be in two different vec's. When the value of Cell changes I want that Cell to send a signal to each of its vec so that each vec can deal with the change in Cell. Right now I have a class Grid and the cell's event is returned through vec event_handler and that is returned to Grid event_handler. How can I have a pointer in Cell to point to vec? I have read of using dynamic pointers but I'm not sure on the syntax but I have also read that using a dynamic pointer is a flaw in C++ and shouldn't realy be use. Or is there another way to deal with my situation?

Thanks,
Milton

grumpy · Jan 4th, 2006, 10:56 PM

Look up forward declarations.

In Cell.h

(Toggle Plain Text)

class vec;   //forward declaration

class Cell
{
     public:

           void SetParent(vec *the_parent) {parent = the_parent;};
           void event_handler();
     private:
         vec *parent;
};

In vec.h, you can also do a similar thing;

(Toggle Plain Text)

class Cell;   //forward declaration

class vec{
private:
  Cell* array[10];
public:
  void set_array(Cell* in);
  int  event_handler(void);
  //other code
};

Now, in the implementation of the Cell class (eg cell.cpp) you need to include both headers, so you can call members from either class;

(Toggle Plain Text)

#include "vec.h"
#include "Cell.h"

void Cell::event_handler()
{
    parent->event_handler();
}

The implementation of Cell::handler cannot be placed in a header file, as a forward declaration of a class vec is insufficient to allow a member function of vec to be called.

This should be enough to get you started ....

ionexchange · Jan 5th, 2006, 5:22 PM

Thanks. I'll work with it.

Milt

Jan 4th, 2006, 10:30 PM	#1
ionexchange Newbie Join Date: Oct 2005 Posts: 12 Rep Power: 0	pointer in base class to derived class So I have this grid and it is made up of cells (Toggle Plain Text) class Cell{ private: int value; public: void set_value(int in); int get_value(void); int event_handler(void); // other code }; class Cell{ private: int value; public: void set_value(int in); int get_value(void); int event_handler(void); // other code }; This grid is made up row and columns which are the same type (Toggle Plain Text) class vec{ private: Cell* array[10]; public: void set_array(Cell* in); int event_handler(void); //other code }; class Grid{ private: vec[100]; public: void event_handler(void); // and other code }; class vec{ private: Cell* array[10]; public: void set_array(Cell* in); int event_handler(void); //other code }; class Grid{ private: vec[100]; public: void event_handler(void); // and other code }; Vec contains and array of pointers to cell so I use vect to controll the behavior of the cell in vec. It is possible, howerver that the address (or controll of a cell) can be in two different vec's. When the value of Cell changes I want that Cell to send a signal to each of its vec so that each vec can deal with the change in Cell. Right now I have a class Grid and the cell's event is returned through vec event_handler and that is returned to Grid event_handler. How can I have a pointer in Cell to point to vec? I have read of using dynamic pointers but I'm not sure on the syntax but I have also read that using a dynamic pointer is a flaw in C++ and shouldn't realy be use. Or is there another way to deal with my situation? Thanks, Milton

Jan 4th, 2006, 10:56 PM	#2
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,221 Rep Power: 5	Look up forward declarations. In Cell.h (Toggle Plain Text) class vec; //forward declaration class Cell { public: void SetParent(vec the_parent) {parent = the_parent;}; void event_handler(); private: vec parent; }; class vec; //forward declaration class Cell { public: void SetParent(vec the_parent) {parent = the_parent;}; void event_handler(); private: vec parent; }; In vec.h, you can also do a similar thing; (Toggle Plain Text) class Cell; //forward declaration class vec{ private: Cell* array[10]; public: void set_array(Cell* in); int event_handler(void); //other code }; class Cell; //forward declaration class vec{ private: Cell* array[10]; public: void set_array(Cell* in); int event_handler(void); //other code }; Now, in the implementation of the Cell class (eg cell.cpp) you need to include both headers, so you can call members from either class; (Toggle Plain Text) #include "vec.h" #include "Cell.h" void Cell::event_handler() { parent->event_handler(); } #include "vec.h" #include "Cell.h" void Cell::event_handler() { parent->event_handler(); } The implementation of Cell::handler cannot be placed in a header file, as a forward declaration of a class vec is insufficient to allow a member function of vec to be called. This should be enough to get you started ....

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Jan 5th, 2006, 5:22 PM	#3
ionexchange Newbie Join Date: Oct 2005 Posts: 12 Rep Power: 0	Thanks. I'll work with it. Milt

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Programming Forums > Application Development > C++

pointer in base class to derived class