Question

我试图组织我的项目所以我认为我将在global.h头中包含我的所有全局变量#includes和struct definition。但是我无法完全理解这个概念，并且构建期间的错误似乎证明了这一点。当我尝试在logic.h中访问我的global.h时，会发生这种情况。

global.h：

#ifndef GLOBAL_H
#define GLOBAL_H
#include "logic.h"
#include <SDL.h>
#include <iostream>
#include <string>
#include "graphics.h"

//Global variables and structs
enum directions
{
    D_UP,
    D_LEFT,
    D_DOWN,
    D_RIGHT,
    D_TOTAL
};

struct Character
{
    float health;
    float x;
    float y;
    float velocity;
    bool collision[D_TOTAL];
    directions direction;
    SDL_Rect animation;
    SDL_Rect sprite;
};

const int windowWidth = 800;
const int windowHeight = 600;
const int frameWidth = 64;
const int frameHeight = 64;
#endif // GLOBAL_H

logic.h：

#include "global.h"
//Header for gamelogic functions

//Initialization of all variables for a new character
void initCharacter(Character &newCharacter, float x, float y, directions startingDirection);

当我尝试构建它时，这就是我得到的错误：

||=== Build: Debug in GameProject0.2 (compiler: GNU GCC Compiler) ===|
C:\Users\Rafał\Documents\GameProject0.2\GameProject0.2\logic.h|5|error: variable or field 'initCharacter' declared void|
C:\Users\Rafał\Documents\GameProject0.2\GameProject0.2\logic.h|5|error: 'Character' was not declared in this scope|
C:\Users\Rafał\Documents\GameProject0.2\GameProject0.2\logic.h|5|error: 'newCharacter' was not declared in this scope|
C:\Users\Rafał\Documents\GameProject0.2\GameProject0.2\logic.h|5|error: expected primary-expression before 'float'|
C:\Users\Rafał\Documents\GameProject0.2\GameProject0.2\logic.h|5|error: expected primary-expression before 'float'|
C:\Users\Rafał\Documents\GameProject0.2\GameProject0.2\logic.h|5|error: 'directions' was not declared in this scope|
||=== Build failed: 6 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|

我不确定我错过了什么。谢谢你的建议！

Answer 1

当你include "global.h"时，其中一个第一个事情就是include "logic.h"，所以处理器会打开该文件，找到一个include "global.h"，它什么都不做因为包含守卫，然后它找到void initCharacter(Character &newCharacter,并且因为它还不知道Character是什么而感到困惑。然后它返回包含，lexes enum directions，然后最后 lexes struct Character，所以然后它知道Character是什么，太晚了。

一般来说，尽量确保只包含一种方式。请确保logic包含global，或global包括logic，但不能同时包含global。

或者，如果你真的很懒，有一个技巧有时会回避这个问题：尽可能经常地在包含之前放置函数和类定义。然后class Character将告诉编译器logic.h存在，然后当它包含#ifndef GLOBAL_H #define GLOBAL_H enum directions; struct Character; //If you're really lazy, this usually works #include "logic.h" #include <SDL.h> #include <iostream> #include <string> #include "graphics.h" //Global variables and structs enum directions { D_UP, D_LEFT, D_DOWN, D_RIGHT, D_TOTAL }; struct Character { ...时，它就不会有问题。

void generate(){
    std::vector<std::thread> threads;
    for(size_t i=0; i<10; i++){
        threads.push_back(std::thread(move_column_blocks, 1, 2));
        threads.push_back(std::thread(move_column_blocks, 2, 3));
    }

    for(auto& t : threads)
        t.join();
}

C ++ struct在单独的头文件中

1 个答案: