在 C++ 中定义 Class 的问题

Question

我是 C++ 编程新手，但有 Java 编程背景。我正在尝试使用 .cpp 和 .h 文件创建 Class，以便它们可以包含在任何项目中。在下面实施以下代码后，我收到多个错误，例如 "use of undefined type 'SUN'" 和 'zsizei: undeclared identifier'。据我所知，我在实现中完全遵循了各种教程和参考资料，但我确信我的代码中存在错误，否则我不会有任何问题。

这里是sun.h:

#ifndef SUN_H
#define SUN_H

class Sun {
public:
    void init(float xsize, float ysize, float zsize);
    void draw();
private:
    float xsizei; //size of interior
    float ysizei; //size of interior
    float zsizei; //size of interior

    float xsizee; //size of exterior
    float ysizee; //size of exterior
    float zsizee; //size of exterior

    float xySlices;
    float yzSlices;
    float thetaXY;
    float thetaYZ;

        float ratio;
    };

#endif

这里是sun.cpp:

#ifdef _APPLE_
#  include <GL/glew.h>
#  include <GL/freeglut.h>
#  include <OpenGL/glext.h>
#else
#  include <GL/glew.h>
#  include <GL/freeglut.h>
//#  include <GL/glext.h>
#pragma comment(lib, "glew32.lib") 
#endif

# include <math.h>
# include "sun.h"

# define PI 3.141569

class Sun {
public:
    void init(float xsize, float ysize, float zsize);
    void draw();
private:
    float xsizei; //size of interior
    float ysizei; //size of interior
    float zsizei; //size of interior

    float xsizee; //size of exterior
    float ysizee; //size of exterior
    float zsizee; //size of exterior

    float xySlices = 36;
    float yzSlices = 36;
    float thetaXY = xySlices / (2 * PI);
    float thetaYZ = yzSlices / (2 * PI);

    float ratio = 0.8;
};

/**
* Object will be drawn with its origin in its center
*/
void Sun::init(float xs, float ys, float zs) {
    xsizei = xs * ratio;
    ysizei = ys * ratio;
    zsizei = zs * ratio;

    xsizee = xs * (1 - ratio);
    ysizee = ys * (1 - ratio);
    zsizee = zs * (1 - ratio);
}

/*
* Draw this object
*/
void Sun::draw() {
    //first, draw the ball part
    for (int i = 0; i < xySlices; i++) {

        float yStart = ysizei / 2 * sin(thetaYZ * i);
        float yEnd = ysizei / 2 * sin(thetaYZ * (i + 1));

        float zStart = zsizei / 2 * sin(thetaYZ * i);
        float zEnd = zsizei / 2 * sin(thetaYZ * (i + 1));

        for (int j = 0; j < yzSlices; j++) {
            float xStart = xsizei / 2 * cos(thetaXY * j);
            float xEnd = xsizei / 2 * cos(thetaXY * (j + 1));

            glVertex3f(xStart, yStart, zStart);
            glVertex3f(xStart, yEnd, zEnd);
            glVertex3f(xEnd, yEnd, zEnd);

            glVertex3f(xEnd, yEnd, zEnd);
            glVertex3f(xEnd, yStart, zStart);
            glVertex3f(xStart, yStart, zStart);
        }

    }
}

我想我可能会重复声明，所以我尝试省略 sun.cpp 中已经声明的内容，但这并没有解决问题。

这是我收到的错误消息：

Severity    Code    Description Project File    Line    Suppression State
Error   C2065   'ratio': undeclared identifier  Proj    c:\sun.cpp 48  
Error   C2027   use of undefined type 'Sun' Proj    c:\sun.cpp 41  
Error   C2027   use of undefined type 'Sun' Proj    c:\sun.cpp 54  
Error   C2065   'zsizei': undeclared identifier Proj    c:\sun.cpp 44  
Error   C2065   'zsizei': undeclared identifier Proj    c:\sun.cpp 61  
Error   C2065   'zsizei': undeclared identifier Proj    c:\sun.cpp 62  
Error   C2065   'zsizee': undeclared identifier Proj    c:\sun.cpp 48  
Error   C2065   'yzSlices': undeclared identifier   Proj    c:\sun.cpp 64  
Error   C2065   'ysizei': undeclared identifier Proj    c:\sun.cpp 43  
Error   C2065   'ysizei': undeclared identifier Proj    c:\sun.cpp 58  
Error   C2065   'ysizei': undeclared identifier Proj    c:\sun.cpp 59  
Error   C2065   'ysizee': undeclared identifier Proj    c:\sun.cpp 47  
Error   C2065   'xySlices': undeclared identifier   Proj    c:\sun.cpp 56  
Error   C2065   'xsizei': undeclared identifier Proj    c:\sun.cpp 42  
Error   C2065   'xsizei': undeclared identifier Proj    c:\s...

Answer 1

您正在 cpp 中重新声明太阳 class。 #include 本质上是复制和粘贴头文件。因此，您正在创建两个具有相同 class 名称的声明，而编译器不知道选择哪一个。从 cpp 中删除 class 声明，它应该可以工作。

Answer 2

问题是您的 .cpp 文件正在重新声明太阳 class。相反，您需要的是从 .cpp.

中删除 class Sun

要实现 .h/.cpp 格式，您可以这样做：

在.h

#ifndef SUN_H
#define SUN_H
class Sun { 
int x;
public : 
    void foo(int);
}
#endif

在 .cpp 中

#include "sun.h"

//define the function no need to write class sun again
void foo(int s) {
x = s;
}

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