C++ inheritance subclass modifiable variables - c++

Question

Help me understand how to use the superclass variable in the subclass and being able to make changes to it, I am making a clone Space Invaders 2D game using SDL library
First off I have a Rectangle class that is inherited from SDL_Rect looking like this i'll leave the unimportant parts out
//Rectangle.h
namespace galaxy{
struct Rectangle : public SDL_Rect{
Rectangle();
Rectangle(int xx, int yy, int hh, int ww);
Rectangel centeredRect(int width, int height) const
bool overlaps(const Rectangle& other) const;
};
}
I'll leave the .cpp out because it's fairly easy to see what part the rectangel is playing in this and I don't want to bore you guys out,
Then I have a Sprite class that is the superclass of the figures in the game,
namespace galaxy{
class Sprite{
public:
virtual void draw() = 0;
virtual ~Sprite();
virtual void keyLeft(SDLKey k);
virtual void keyRight(SDLKey k);
......more buttons
protected:
Sprite(int x, int y, int h, int w);
private:
Rectangle rect;
Sprite (const Sprite&);
const Sprite& operator=(const Sprite&);
};
}
In the .cpp file I have the following code
namespace galaxy{
Sprite::Sprite{int x, int y, int h , int w) : rect (x, y, h, w){}
Sprite::~Sprite(){}
const Rectangel& Sprite::getRect() const{
return rect;
}
void Sprite::keyLeft(SDLKey k){}
void Sprite::keyRight(SDLKey k){}
void Sprite::keyDown(SDLKey k){}
...more buttons
}
Then to where the problem is, I have another class Ship, where I want to overload the keyLeft from the superclass, having the rectangle rect following with coordinates, and I need to change the x, and y in the subclass, but when doing so with the construction I have below the r.x++; is behaving as inside a function and the changes to rectangle x is being cleared when exiting the function, when trying to reach rect in Ship class I get error not reachable, when getting rect through r = getRect(); the change to r is only inside the function but the ship does not move on screen.
//Ship.h
namespace galaxy {
class Ship : public Sprite{
public:
void keyLeft(SDLKey k);
void keyRight(SDLKey k);
void keyDown(SDLKey k);
void keyUp(SDLKey k);
void space(SDLKey k);
Ship(int x, int y, int hits);
private:
SDL_Surface* ship;
int hits;
};
}
//Ship.cpp
using namespace std;
namespace galaxy{
Rectangel r;
Ship::Ship(int x, int y, int hits) : Sprite(x, y, NULL, NULL), hits(hits){
ship = IMG_Load("Ship.png");
}
//Here is where my problem is.....
void Ship::keyLeft(SDLKey k){
std::cout << "Im here!\n";
std::cout << r.getX(); // outputs 250
r.x--;
std::cout << r.getX(); // outputs 251
}
void Ship::keyRight(SDLKey k){
std::cout << "Im here!\n";
}
void Ship::keyDown(SDLKey k){
std::cout << "Im here!\n";
}
void Ship::keyUp(SDLKey k){
std::cout << "Im here!\n";
}
void Ship::space(SDLKey k){
std::cout << "Im here!\n";
}
void Ship::draw(){
r = getRect();
SDL_BlitSurface(ship, NULL, sys.screen, &r);
}
}
right now Im doing this like:
#ifndef SHIP_H
#define SHIP_H
#include "Sprite.h"
#include <string>
namespace galaxy {
class Ship : public Sprite{
public:
/*static Ship* getInstance(int x, int y, int hits);*/
void draw();
//virtual void perform() = 0;
/*int getHits() const;*/
int getX() const;
int getY() const;
const Rectangel& getRect() const;
void keyLeft(SDLKey k);
void keyRight(SDLKey k);
void keyDown(SDLKey k);
void keyUp(SDLKey k);
void space(SDLKey k);
//~Ship();
//protected:
Ship(int x, int y, int hits);
private:
SDL_Surface* ship;
int hits;
Rectangel rect;
};
}
#endif
#include "Ship.h"
#include "Globals.h"
#include "Sprite.h"
#include <SDL_image.h>
#include <iostream>
using namespace std;
namespace galaxy{
Rectangel r;
/*Ship* Ship::getInstance(int x, int y, int hits){
return new Ship(x, y, hits);
}*/
Ship::Ship(int x, int y, int hits) : Sprite(x, y, NULL, NULL), hits(hits){
ship = IMG_Load("Ship.png");
}
const Rectangel& Ship::getRect() const{
return rect;
}
void Ship::keyLeft(SDLKey k){
std::cout << "Im here!\n";
rect.x--;
}
void Ship::keyRight(SDLKey k){
std::cout << "Im here!\n";
}
void Ship::keyDown(SDLKey k){
std::cout << "Im here!\n";
}
void Ship::keyUp(SDLKey k){
std::cout << "Im here!\n";
}
void Ship::space(SDLKey k){
std::cout << "Im here!\n";
}
/* int Ship::getHits() const{
return hits;
}*/
int Ship::getX() const{
return r.getX();
}
int Ship::getY() const{
return r.getY();
}
void Ship::draw(){
r = getRect();
SDL_BlitSurface(ship, NULL, sys.screen, &r);
}
}
But this is just a workaround so that I'm not stuck forever.

Answer 1

If you do something like this:
Rectangel r;
...
r = getRect();
Then you'll just get the original rectangle copied to your r variable, when you change it, the original Rectangel wont change.
Maybe for quick fix you could implement setRect function to your Ship class to be actually able to write back modified data.
void Ship::setRect(const Rectangel& rr) { rect = rr; }

Answer 2

And if you want to reach the rect from the Sprite base class directly then you need to give the rect protected visibility like so:
class Sprite
{
[...]
protected:
Rectangle rect;
[...]
};