C++ 错误 "undefined reference to GPScoord::(double,double) etc."

Question

主.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;
}

全局定位系统.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

全局定位系统

#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不是double还是gps2不是class？我认为这个问题在 gps.h 中，但我没有发现这个错误。

Answer 1

首先，您需要编译这两个源文件，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，正如解释的那样here可以通过在头文件中定义类，然后将类的方法实现到源文件中来修复，而无需重新定义类。

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();
                  ^~~~~~~

这会发生，就像编译器所说的那样，因为某些函数需要标记为 const。把它们放在一起你会得到类似下面的代码:

全局定位系统.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

全局定位系统:

#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;
}