How to use This Keyword and using iterators to call class methods?

Question

I've been over this for a long time, I can't seem to understand what is wrong, is the use of the this keyword right? I want to add the instance of the class that is being created to the vector 'allEntities' in the constructor, or am I not using the iterators right? I'm very new to c++ and programming in general so all help is appreciated.

GameObject.h

class GameObject {

public:
    GameObject(const char* texturesheet, SDL_Renderer* ren, int x, int y, int _maxHp, int _currentHp, int _strength);
    ~GameObject();

    static std::vector<GameObject> allEntities;

    void update();
    void Render();
    void movement(const char* coord, bool positive);
    int getMaxHp();
    void addMaxHp(int change);
    int getCurrentHp();
    void setCurrentHp(int change);
    int getStrength();
    void changeStrength(int change);
    void attack(GameObject &other);
    int getX() { return x; };
    int getY() { return y; };
    void setDirectionFacing(char direction) { directionFacing = direction; };
    char getDirectionFacing() { return directionFacing; };
private:

    int x;
    int y;
    int strength;
    int maxHp;
    int currentHp;
    char directionFacing;


    SDL_Texture* objectTexture;
    SDL_Rect srcRect, destRect;
    SDL_Renderer* renderer;

};

GameObject.cpp

GameObject::GameObject(const char* texturesheet, SDL_Renderer* ren, int xx, int yy, int _maxHp, int _currentHp, int _strength)
{
    allEntities.push_back(*this);
    renderer = ren;
    objectTexture = textureCreator::loadTexture(texturesheet, ren);
    GameObject::maxHp = _maxHp;
    GameObject::currentHp = _currentHp;
    changeStrength(_strength);
    x = xx;
    y = yy;
}
GameObject::~GameObject()
{

}

void GameObject::update()
{



    srcRect.h = 48;
    srcRect.w = 48;
    srcRect.x = 0;
    srcRect.y = 0;


    destRect.x = x;
    destRect.y = y;
    destRect.w = srcRect.w * 1.5;
    destRect.h = srcRect.h * 1.5;
}

void GameObject::movement(const char* coord, bool positive)
{

    if (coord == "x" && positive == true) 
    { 
        y -= 4;
        setDirectionFacing('w');
        std::cout << 'w' << std::endl;
    };
    if (coord == "x" && positive == false) 
    { 
        y += 4; 
        setDirectionFacing('s');
        std::cout << 's' << std::endl;
    };
    if (coord == "y" && positive == true) 
    { 
        x += 4;
        setDirectionFacing('d');
        std::cout << 'd' << std::endl;
    };
    if (coord == "y" && positive == false) 
    { 
        x -= 4; 
        setDirectionFacing('a');
        std::cout << 'a' << std::endl;

    };


}

void GameObject::Render()
{
    SDL_RenderCopy(renderer, objectTexture, &srcRect, &destRect);
}

int GameObject::getCurrentHp() { return currentHp; };

int GameObject::getMaxHp() { return maxHp; };

void GameObject::setCurrentHp(int change) { currentHp += change; };

void GameObject::addMaxHp(int change) { maxHp += change; };

int GameObject::getStrength() { return strength; }

void GameObject::changeStrength(int change) { strength += change; }

void GameObject::attack(GameObject &other) 
{


}

game.cpp

GameObject* player;
player = new GameObject("player.png", renderer, 10 , 10, 10,  10, 2);
    for (std::vector<GameObject>::iterator it = GameObject::allEntities.begin(); it != GameObject::allEntities.end(); it++) {
        int hp = it->getCurrentHp();
        std::cout << hp << std::endl;
    }

I expect to print out the hp value which is 10, but instead it prints 0 instead.

Also I need this vector so when the player attacks, it checks every entity and sees if it is in the area of the attack in a for loop, is there any better way to do this?

Answer 1

These two lines in the constructor do not do what you think they do:

GameObject::maxHp = _maxHp;
GameObject::currentHp = _currentHp;

In the constructor, as in any class method, you access the class variables directly, like so:

maxHp = _maxHp;
currentHp = _currentHp;

Most compilers would probably catch this as a warning, and especially while learning I would recommend turning up your compiler warnings as high as they go, just on the general principle of getting a feeling for what the compiler is doing.

You need one more change because this line creates a shallow copy of the object being constructed and adds that copy to the allEntities vector, and it does that copy before any member variables have been set.

allEntities.push_back(*this);

I think that if you move that line after all the variables have been set then you're done. With a note: what you probably want to do later is make allEntities a vector of pointers to created objects and not a full copy, but since you're very new that can come later.

Also, for problems like this there's a technique called Rubber Duck Debugging that is very helpful https://en.wikipedia.org/wiki/Rubber_duck_debugging