"expected class name before '{' token" and "invalid use of incomplete type 'class CentralClass'"

Question

I am rewriting the mouse input tutorial on lazyfoo.net to use headers and cpp files instead of putting everything in one cpp file. I am doing this just for practice. I am running Windows 10 and I am using Code::Blocks 16.01 on a Dell laptop.

When I compile the following source code I get an error message that says "expected class name before '{' token" in my ltexture.h file. I have tried forward declaring CentralClass in my ltexture.h file and when I do that I get an error message that says "invalid use of incomplete type 'class CentralClass'". I have also looked up several answers to this same question on this website but nothing seems to work.

Here is the code.

ltexture.h

    #ifndef LTEXTURE_H_INCLUDED
#define LTEXTURE_H_INCLUDED

#include <string>
#include "central_class.h"

class LTexture : public CentralClass
{
    // The actual hardware texture
    SDL_Texture *mTexture;

    // Image dimensions
    int mWidth;
    int mHeight;

public:
    // Initialize variables
    LTexture();

    // Deallocates memory
    ~LTexture();

    // Loads image at specified path
    bool loadFromFile(std::string path);

    // Deallocates texture
    void free();

    // Renders texture at given point
    void render(int x, int y, SDL_Rect *clip = nullptr, double angle = 0, SDL_Point *center = nullptr, SDL_RendererFlip flip = SDL_FLIP_NONE);

    // Gets image dimensions
    int getWidth() {return mWidth;}
    int getHeight() {return mHeight;}
};

#endif // LTEXTURE_H_INCLUDED

central_class.h

    #ifndef CENTRAL_CLASS_H_INCLUDED
#define CENTRAL_CLASS_H_INCLUDED

#include <SDL.h>
#include "lButtonSprite.h"
#include "lbutton.h"
#include "ltexture.h"
#include "global.h"

class CentralClass
{
    // The window we'll be rendering to
    SDL_Window *mWindow;

    // Button objects
    LButton mButtons[global::TOTAL_BUTTONS];

protected:
    // The window renderer
    SDL_Renderer *mRenderer;

    // Mouse button sprites
    SDL_Rect mSpriteClips[button::TOTAL];
    LTexture mButtonSpriteSheetTexture;

public:
    // Call all functions
    CentralClass();

    // Starts up SDL and creates window
    bool init();

    // Loads media
    bool loadMedia();

    // Main part of the program
    void mainLoop();

    // Frees media and shuts down SDL
    void close();

    // Clean up
    ~CentralClass();
};

#endif // CENTRAL_CLASS_H_INCLUDED

Both of these classes depend on eachother. Please help get rid of these errors. I don't know what to do.enter code here

Answer 1

Both files include the other one, which would result in an indefinite loop (this is prohibited by the #define).

Either way, one of them misses the class definition of the other one. The only way to resolve that is a forward declaration.

To fix it, enter class xxx; in either (or both) files, referring to respectively the other class.

In addition, there is a logical error in the structure, as class 1 contains an object of class 2, and class 2 is derived from class 1 (so it contains an object of class 1). Obviously, a class cannot contain an object of itself; that would be infinite recursive definition. I assume the class inside the other is supposed to be a pointer to an object, not an object.