将Netbeans（C ++）与G ++一起使用时出现未定义的参考错误

Question

I'm working on this since hours and I believe I overlooked something. I'm new to C++ and programming in general. I'm trying to build a program which consists of several .cpp-files. The associated headerfiles are in an include-directory. I've of course also told netbeans where to search for them (Project >> Properties >> build >> C++-Compiler >> include directories).

That's the main-file:

//main.cpp

#include "Eingabe_Konstanten.h"
#include "Stoffwerte.h"
#include "Zustandsgroessen.h"
#include <iostream>

using namespace std;

int main()
{
    Eingabe_Konstanten ein;
    cout << ein.Pi();
    cin.get();
}

And that's the associated headerfile "Eingabe_Konstanten.h" (sorry, it's partly german... ;))

//Eingabe_Konstanten.h

#ifndef EINGABE_KONSTANTEN_H
#define EINGABE_KONSTANTEN_H

class Eingabe_Konstanten {
public:
    double Pi();
    double mStrom();
};

#endif  /* EINGABE_KONSTANTEN_H */

With the corresponding .cpp-file

//Eingabe_Konstanten.cpp

#include "Eingabe_Konstanten.h"
#include "InputOutput.h"
#include <string>

InputOutput io;

double Pi()
{
    double pi = M_PI;
    return pi;
}

double mStrom()
{
    double m = io.lese(7);
    return m;
}

lese() is a method which reads lines from a file. It's in an InputOutput Class.

//InputOutput.h

#ifndef INPUTOUTPUT_H
#define INPUTOUTPUT_H
#include <string>

class InputOutput {
public:
    double lese(int);
};

#endif  /* INPUTOUTPUT_H */

*************************************

//InputOutput.cpp

#include "InputOutput.h"
#include <iostream>
#include <string>
#include <sstream>
#include <limits>
#include <fstream>
#include <stdlib.h>

using namespace std;

double lese(int zeile) 
{
    ifstream datei("input.txt"); 
    if(!datei.is_open()) 
    { 
        cerr << "Fehler beim Oeffnen der Datei" << endl; 
        return 0; 
    } 
    for(; zeile > 1; --zeile) 
        datei.ignore(numeric_limits<streamsize>::max(), '\n'); 
        string input;
    if(!getline(datei, input)) 
    { 
        cerr << "Fehler beim Lesen aus der Datei" << endl; 
        return 0; 
    }
        double wert = atof(input.c_str());
    return wert; 
}

I think it's a linking problem. Because the object files don't seem to be linked correctly together and the compiler doesn't complain until the linking process. The output looks like this:

"/C/MinGW/msys/1.0/bin/make.exe" -f nbproject/Makefile-Debug.mk QMAKE= SUBPROJECTS= .build-conf
make.exe[1]: Entering directory `/d/Maschinenbau/Diplom/Diplomarbeit/Programm/Comp_Pred'
"/C/MinGW/msys/1.0/bin/make.exe"  -f nbproject/Makefile-Debug.mk dist/Debug/MinGW_TDM-Windows/comp_pred.exe
make.exe[2]: Entering directory `/d/Maschinenbau/Diplom/Diplomarbeit/Programm/Comp_Pred'
mkdir -p dist/Debug/MinGW_TDM-Windows

g++ -m32    -o dist/Debug/MinGW_TDM-Windows/comp_pred build/Debug/MinGW_TDM-Windows/_ext/725510466/Eingabe_Konstanten.o build/Debug/MinGW_TDM-Windows/_ext/725510466/InputOutput.o build/Debug/MinGW_TDM-Windows/_ext/725510466/Stoffwerte.o build/Debug/MinGW_TDM-Windows/_ext/725510466/Zustandsgroessen.o build/Debug/MinGW_TDM-Windows/main.o -Llib -lCoolProp
build/Debug/MinGW_TDM-Windows/_ext/725510466/Eingabe_Konstanten.o: In function `Z6mStromv':
d:/Maschinenbau/Diplom/Diplomarbeit/Programm/Comp_Pred/Eingabe_Konstanten.cpp:24: undefined reference to `InputOutput::lese(int)'

I'm sorry for this comprehensive description, but I really don't know what to do. I would be very grateful for any help.

Answer 1

You have defined your lese() function as a freestanding function, but you need it to be a member of your InputOutput class. So

double lese(int zeile) 

should be

double InputOutput::lese(int zeile) 

The same goes for the functions of your Eingabe_Konstanten class