Unreachable base class

Question

I am writing a simple game in SDL. I have a class hierarchy that I create for any sprite that I use in the game. The base class is Sprite, which contains data abstractions for the collision and sprite window. Immediately below are two abstract classes: Character and MapObject.

I am currently implementing the Player class, which is derived from Character (Enemy and NPC will also be derived from the abstract Character class).

In any case, I hope this makes sense. My problem is this:

When I try to use the player class in the engine, I cannot access any of the Sprite features.

I get the following error:

'Sprite' is not an accessible base of 'Player' 

Here are the header files:

Sprite.h:

 class Sprite{ public: virtual ~Sprite() = 0; //I want this to be an abstract class and yes this is defined in the cpp //Initialization functions - MUST be called before anything else in the class can be used. void setupCollider(int xo, int yo, int ho, int wo); void setupSheet(SDL_Surface* dest, std::string file, int numClips, int ac, int _res, int sr); //SpriteSheet functions void setActiveClip(int a); int getActiveClip() const; void draw() const; int getResolution() const; SDL_Surface* getDest(); //Collider functions void updateCollider(); SDL_Rect box() const; bool collision(SDL_Rect other) const; //Access and Modify coordinates of the sprite void setLoc(int x, int y) { _x = x; _y = y; } int getX() const { return _x; } int getY() const { return _y; } private: struct Collider{ SDL_Rect _box; int x_offset, y_offset; }; struct SpriteSheet{ SDL_Surface* destination; SDL_Surface* sheet; SDL_Rect* clips; int _numClips; int active; int res; int sheetrows; }; Collider collisionAttributes; SpriteSheet spriteSheetAttributes; int _x, _y; }; 

Character.h:

 class Character : public Sprite{ public: virtual void move(Direction direction_input, const TileMap& currentlevel) = 0; virtual void animate() = 0; virtual void setAttributes( int h, int sp, int ad, int d, int m, int md, int l, std::string n){ hearts = h; speed = sp; attackdamage = ad; defense = d; magicdamage = m; magicdefense = md; level = l; name = n; } bool isDead() const{ return hearts == 0; } void heal(int heartsup){ hearts += heartsup; } void dealDamage(int heartsDown){ hearts -= heartsDown; } protected: int hearts; int speed; int attackdamage; int defense; int magicdamage; int magicdefense; int level; std::string name; }; 

Player.h:

 //Not fully finished yet, but should work for the purposes of this question class Player : protected Character{ public: ~Player(){ if(heart) SDL_FreeSurface(heart); } static const int HEART_WIDTH; void move(Direction direction_input, const TileMap& currentlevel); void animate(); void updateCamera(TileMap& currLevel); private: SDL_Surface* heart; enum ClipFace { UP1, UP2, DOWN1, DOWN2, LEFT1, LEFT2, RIGHT1, RIGHT2 }; static const std::string HEART; static const int HEART_RES; }; 

I get the first error in my engine when I try to call the configuration functions from Sprite in the player, the first of which:

 player.setLoc(levels[0].startX(), levels[0].startY()); 

Any help is appreciated.

[SOLVED] EDIT: alternative comment solution: the character class did not inherit anything from the Sprite class, so technically it did not need to be derived from it. Instead of inheriting Character from Sprite, I had a Player inheriting from BOTH Sprite and Character, and it also worked. I am not sure if this is the best design.

Answer 1

I think you need to change

 class Player : protected Character{ 

to

 class Player : public Character{ 

In this way, you can access the Character and Sprite functions of the Player object from a Player instance created anywhere in your program.

If a Player can do anything that Character can do, public inheritance makes sense. There is no reason to hide something in Player that is freely available in Character or Sprite objects.

Answer 2

Always use public inheritance to represent the is-a relationship. Player seems to be Character , so inheritance should be public , not protected .

Inheritance

protected and private inherit more as a "has-a" (and in most cases, a member subobject is an easier way to handle this relationship).

Answer 3

I would say that since Character is a protected base class, it restricts access to Sprite .