c++ 错误“未定义对 GPScoord::(double,double) 等的引用”

Question

main.cc

#include <iostream>
#include <cstdlib>
#include <string>
#include "gps.h"

using namespace std;

int main(int argc, char  *argv[])
{

  GPScoord  gps1(12.0,13.0);
  GPScoord  gps2(12.0,13.0);

  cout<<gps1.distance_to(gps2)<<endl;

  return 0;
}

gps.h

#ifndef GPS_H
#define GPS_H

class GPScoord {
  public:
  GPScoord(double lat, double longt);

  double lattitude1();
  double longtitude1();
  double rad_lat();
  double rad_long();
  double  distance_to(const GPScoord&  gps );
  private:
  double lattitude;
  double longtitude;
};

#endif

gps.cc

#include <cstdlib>
#include <iostream>
#include <cmath>
#include <math.h>
#include "gps.h"
using namespace  std;

class GPScoord 
{
  private:
  double lattitude;
  double longtitude;
  public:
    GPScoord(double lat,double longt) {

    lattitude=lat;
    longtitude=longt;
  }

  public:
  double lattitude1(){ return lattitude; }
  double longtitude1(){ return longtitude; }
  double rad_lat(){ return lattitude*M_PI/180; }
  double rad_long(){ return longtitude*M_PI/180; }

  double  distance_to(const GPScoord&   gps ){
  double R = 6371e3;
  double radlat = rad_lat();
  double ralong = rad_long();
  double radlat1 = gps.rad_lat();
  double radlong1 = gps.rad_long();
  double radlat2 = radlat-radlat1;
  double radlong2 = ralong-radlong1;
  double          a = pow((sin(radlat2/2)),2)+cos(radlat)*
  cos(radlat1)*pow((sin(radlong2)),2);
  double c=2*atan2(sqrt(a),sqrt(1-a));
  return R*c;
}

};

我收到以下错误：

/tmp/cc13HrVO.o: In function `main':
/home/mustafa/Desktop/main.cc:14: undefined reference to     `GPScoord::GPScoord(double, double)'
/home/mustafa/Desktop/main.cc:15: undefined reference to       `GPScoord::GPScoord(double, double)'
/home/mustafa/Desktop/main.cc:17: undefined reference to   `GPScoord::distance_to(GPScoord const&)'
collect2: error: ld returned 1 exit status

我没看懂这个错误，12.0 is not double or gps2 is not class？ 我认为这个问题在 gps.h 但我没有发现这个错误。

Answer 1

首先，您需要编译两个源文件，如下所示：

g++ -Wall main.cc gps.cc

然后你会看到你收到一个重新定义你的类的错误，正如here解释的那样，可以通过在头文件中定义类然后将你的类的方法实现到源文件来修复，而不必重新定义类。

之后你会得到这样的错误：

gps.cc:21:19: error: member function 'rad_lat' not viable: 'this' argument has
      type 'const GPScoord', but function is not marked const
  double radlat = rad_lat();
                  ^~~~~~~

正如编译器所说，因为某些函数需要标记为 const。将它们放在一起，您将得到如下代码：

gps.h：

#ifndef GPS_H
#define GPS_H

class GPScoord {
  public:
  GPScoord(double lat, double longt);

  double lattitude1();
  double longtitude1();
  double rad_lat() const;
  double rad_long() const;
  double  distance_to(const GPScoord&  gps ) const;
  private:
  double lattitude;
  double longtitude;
};

#endif

gps.cc：

#include <cstdlib>
#include <iostream>
#include <cmath>
#include <math.h>
#include "gps.h"
using namespace  std;

GPScoord::GPScoord(double lat,double longt) {

    lattitude=lat;
    longtitude=longt;
}

double GPScoord::lattitude1(){ return lattitude; }
double GPScoord::longtitude1(){ return longtitude; }
double GPScoord::rad_lat() const { return lattitude*M_PI/180; }
double GPScoord::rad_long() const { return longtitude*M_PI/180; }

double  GPScoord::distance_to(const GPScoord&   gps ) const {
  double R = 6371e3;
  double radlat = rad_lat();
  double ralong = rad_long();
  double radlat1 = gps.rad_lat();
  double radlong1 = gps.rad_long();
  double radlat2 = radlat-radlat1;
  double radlong2 = ralong-radlong1;
  double          a = pow((sin(radlat2/2)),2)+cos(radlat)*
  cos(radlat1)*pow((sin(radlong2)),2);
  double c=2*atan2(sqrt(a),sqrt(1-a));
  return R*c;
}