ISO C++禁止声明“游戏”，没有类型-可能包含问题？

编译器输出：

g++ -Wall -g main.cpp `sdl-config --cflags --libs` -lSDL_mixer
In file included from Game.h:8,
                 from main.cpp:1:
DrawableObject.h:11: error: ISO C++ forbids declaration of ‘Game’ with no type
DrawableObject.h:11: error: expected ‘;’ before ‘*’ token
DrawableObject.h:13: error: expected ‘)’ before ‘*’ token
main.cpp:7: error: expected ‘}’ at end of input
main.cpp:7: error: expected unqualified-id at end of input
make: *** [all] Error 1
brett@brett-laptop:~/Desktop/SDL$ make
g++ -Wall -g main.cpp `sdl-config --cflags --libs` -lSDL_mixer
In file included from Game.h:8,
                 from main.cpp:1:
DrawableObject.h:11: error: ISO C++ forbids declaration of ‘Game’ with no type
DrawableObject.h:11: error: expected ‘;’ before ‘*’ token
DrawableObject.h:13: error: expected ‘)’ before ‘*’ token
main.cpp:7: error: expected ‘}’ at end of input
main.cpp:7: error: expected unqualified-id at end of input
make: *** [all] Error 1

main.cpp：

#include "Game.h"

int main()
{
    Game g;
    return 0;
}

游戏h：

#ifndef GAME_H
#define GAME_H

#include <cmath>
#include "SDL.h"
#include <vector>
#include "DrawableObject.h"

typedef unsigned char uint8;
typedef unsigned short uint16;
typedef unsigned int uint32;

class Game
{
public:

    SDL_Surface * screen;
    std::vector<DrawableObject*> sprites;

    Game()
    {   
        if (SDL_Init(SDL_INIT_VIDEO) != 0)
            return;

        atexit(SDL_Quit);
        screen = SDL_SetVideoMode(640, 480, 0, SDL_DOUBLEBUF);

        if (screen == NULL)
            return;

        while (true)
        {
            SDL_Event * event;
            while(SDL_PollEvent(event))
            {
                if(event->type == SDL_QUIT)
                    return;
            }

            SDL_LockSurface(screen);

            for (uint32 i=0; i<sprites.size(); ++i)
            {
                sprites[i]->update(event);
            }

            SDL_FreeSurface(screen);
            SDL_Flip(screen);
    }
};

#endif

---

问题是你在游戏中缺少了while循环的结束括号

更新：正如其他人提到的，您还需要解决DrawableObject.h中Game.h的循环包含问题。您只需在DrawableObject标题中声明游戏类型，请参见@ybungalobill和@Lou Franco answers以获取示例

#ifndef GAME_H 
#define GAME_H 

#include <cmath> 
#include "SDL.h" 
#include <vector> 
#include "DrawableObject.h" 

typedef unsigned char uint8; 
typedef unsigned short uint16; 
typedef unsigned int uint32; 

class Game 
{ 
public: 

    SDL_Surface * screen; 
    std::vector<DrawableObject*> sprites; 

    Game() 
    {    
        if (SDL_Init(SDL_INIT_VIDEO) != 0) 
            return; 

        atexit(SDL_Quit); 
        screen = SDL_SetVideoMode(640, 480, 0, SDL_DOUBLEBUF); 

        if (screen == NULL) 
            return; 

        while (true) 
        { 
            SDL_Event * event; 
            while(SDL_PollEvent(event)) 
            { 
                if(event->type == SDL_QUIT) 
                    return; 
            } 

            SDL_LockSurface(screen); 

            for (uint32 i=0; i<sprites.size(); ++i) 
            { 
                sprites[i]->update(event); 
            } 

            SDL_FreeSurface(screen); 
            SDL_Flip(screen); 
        } // This brace is missing
    } 
}; 

#endif 

---

这里有循环依赖关系。当您从main.cpp中包含Game.h并且它包含DrawableObject.h时，后者尝试包含Game.h，但它没有效果，因为Game_h已经定义，但是类Game尚未声明

您需要在DrawableObject.h中使用类游戏的正向声明，如下所示：

// #include "Game.h" <-- remove this since it has no effect
class Game; // <-- forward declaration

class DrawableObject
{
public:
    Game * game;
    // ...
};

---

你可能有一个相互包容的问题。在DrawableObject.h中，更改

#include "Game.h"

到

---

如果只需要指向类的指针和引用，那么向前声明就足够了。

以及@Chris Taylor的答案。它认为你既有这个，也有一个紧闭的大括号，顺便说一句，这是一个错误：SDL_事件*事件；而SDL_PollEventevent。。。没有为事件结构分配内存。你想要SDL_事件；当SDL_轮询事件和事件时。。。

#include "Game.h"

class Game;