c++ - C++中编译类时出现错误

我试图在c++中为3-D vector 创建一个类，但是存在一些错误。我以前在python中学过一点oop，但是对oop和c++还是很新的。我创建了头文件threevector.h，类threevector.cpp的文件和主程序文件main.cpp。我只想知道我做错了什么。

// threevector.h
#ifndef THREEVECTOR_H
#define THREEVECTOR_H
#include <iostream>

class threevector {
    private:
        double xcoord, ycoord, zcoord;

    public:
        threevector();
        threevector(double x, double y, double z, char type);
        void print ();
};
#endif // THREEVECTOR_H


//threevector.cpp
#include "threevector.h"
#include <cmath>

threevector() {
    xcoord = 0.0;
    ycoord = 0.0;
    zcoord = 0.0;
}

threevector(double x, double y, double z, char type) {
    if (type == 'c') {
        // cartesian coordinate
        xcoord = x;
        ycoord = y;
        zcoord = z;
    }
    else if (type == 'p') {
        // polar coordinate
        // x = r, y = phi, z = theta
        xcoord = x*sin(y)*cos(z);
        ycoord = x*sin(y)*sin(z);
        zcoord = x*cos(y);
        }
}

void print () {
    std::cout << xcoord << '\t' << ycoord << '\t' << zcoord << std::endl;
}


// main.cpp
#include "threevector.h"
#include <cmath>
#include <iostream>

using namespace std;

int main() {
    threevector v0;
    v0.print();

    threevector v1(-1,2,4.384,'c');
    cout << "v1 = ";
    v1.print();

    return 0;
}

以下是我收到的错误消息:

main.cpp(.text+0x15): undefined reference to 'threevector::threevector()'
main.cpp(.text+0x15): undefined reference to 'threevector::print()'
main.cpp(.text+0x15): undefined reference to 'threevector::threevector::threevector(double, double, double, char)'
main.cpp(.text+0x15): undefined reference to 'threevector::print()'
[Error] ld returned 1 exit status

最佳答案

您定义了threevector的方法错误。它应该是:

threevector::threevector() {
    xcoord = 0.0;
    ycoord = 0.0;
    zcoord = 0.0;
}

threevector::threevector(double x, double y, double z, char type) {
    if (type == 'c') {
        // cartesian coordinate
        xcoord = x;
        ycoord = y;
        zcoord = z;
    }
    else if (type == 'p') {
        // polar coordinate
        // x = r, y = phi, z = theta
        xcoord = x*sin(y)*cos(z);
        ycoord = x*sin(y)*sin(z);
        zcoord = x*cos(y);
        }
}

void threevector::print () {
    std::cout << xcoord << '\t' << ycoord << '\t' << zcoord << std::endl;
}

所有threevector的方法都在threevector的范围内。

不要忘记像main.cpp一样编译它:

g++ threevector.cpp main.cpp

由于threevector在同一目标文件中，因此将正确链接。

关于c++ - C++中编译类时出现错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/31479863/