Error C2227,C2065, Class within a Class

I'm trying to structure my code like this main <- game <- 开发者_JAVA技巧player.

IF I write in main:

player* P;
P = new player;

P->move();

Everything works but when trying to move this code in to the game component I run in to problems.

Here is the parts of game.cpp I need help with.

#include "game.h"

#include <string>
using namespace std;

game::game(){
    player* P;
    P = new player;
};


void game::playerStuff(){
P->move(); //c2227+C2065
};

Here is a part of game.h

#include "player.h"

class game {

public:

    game();
    void playerStuff();

The issue is rather simple. Your pointer to the player (P) is a local variable only visible/existing within your constructor. Add it as a class member instead to use it everywhere in your game class:

class game
{
    private:
    player *P;
    public:
    game();
    // other stuff ...
}

P needs to be a member of the game class.

Currently, in your constructor here:

game::game(){
    player* P;
    P = new player;
};

P is local to the ctor and disappears as soon as this function ends.

Solution

Make P a member of game:

class game {
private:
    player * P;
public:

    game();
    ~game(); // NOTE: I have added a destructor
    void playerStuff();
}

And change the contructor:

game::game(){
    P = new player;
};

Remembering of course, to delete it in the destructor:

game::~Game(){
    delete P;
};

Of course, because you include <player.h>, you don't need to allocate this object on the heap at all, and can use the stack instead, thereby negating the need to delete P in the destructor.

EDIT: Here is an example showing using the stack, rather than allocating on the heap:

#include "player.h"

class game
{
private:
    player P;  // Note, we're not declaring a pointer.. we have a complete type here.

public:
    game();
    ~game();
    void playerStuff();
}; // eo class game

game.cpp

game::game()
{
   // No need to allocate, it's already allocating on the stack
}; // eo ctor


game::~game()
{
   // No need to delete, P will be deallocated along with this game class.
}; // eo dtor


void game::playerStuff()
{
    P.move();  // note we're not using -> (pointer to member) here
} // eo playerStuff

Move #include "player.h" to game.cpp if you need only pointers or references on game.h. If you need to reference Player on game.h to declare a pointer, you can use a forward declaration, like:

class Player;

class game
{
     Player *myPlayer;
};