Codeblocks c++ undefined reference error, class is defined

Hey guys I asked a question the other day about some c++ code that I couldn't get to work. I took everyones advice as to how to create objects in c++ but now I get undefined reference errors. I am using the latest code blocks version and using that to compile. I have read that this is caused by not linking some files during compilation, and that it means I have defined the class in the header file but not in the code, which confuses me because from my understanding (a profs example) I am declaring the objects.

Header File MathObject.h

class MathObject{
private:
    int num1;
    int num2;

public:
    int sum();
    MathObject(int n, int m);
};

MathObject file MathObject.cpp

#include <iostream>
#include "MathObject.h"
using namespace std;

MathObject :: MathObject(int n, int m){
    num1 = n;
    num2 = m;
}

int MathObject :: sum(){
    return num1+num2;
}

Main File

#include <iostream>
#include "MathObject.h"
using namespace std;

int main(int args, char *argv[]){
    MathObject *mo = new MathObject(3,4);
    int sum = mo -> sum();

    MathObject mo2(3,4);

    //cout << sum << endl;
    return 0;
}

The undefined reference is for all calls to anything in the MathObject class, I have been searching for a small c++ example that I can understand. (The syntax is so different from java)

This used to happen when I tried to use multiple files in c, could this be an issue with my computer?

Upvotes: 1

Answers (6)

Nardos Wehabe

Reputation: 1

To fix undefined reference error :-

Settings -> compiler... -> Build options finally mark "Explicitly add currently compiling file's directory to compiler search dirs"

Upvotes: 0

Hunterrr

Reputation: 1

You can do this simply by adding .cpp file of the class in main.cpp.

#include <iostream>
#include "MathObject.h"
#include "MathObject.cpp"
using namespace std;

int main(int args, char *argv[]){
    MathObject *mo = new MathObject(3,4);
    int sum = mo -> sum();

    MathObject mo2(3,4);

    //cout << sum << endl;
    return 0;
}

Upvotes: 0

impulse

Reputation: 206

Found a solution from code::blocks forum:

-Project -> "Build Options

-Make sure the correct target is highlighted on the left side; if you do not know select the project, top one.

-Select Tab "Search Directories"

-Select Sub-Tab "Compiler"

-"Add" the path to the folder that contains the header. Single Folder per line.

Just add your current folder or location of your header file to the path.

Link: http://forums.codeblocks.org/index.php?topic=14713.0

Upvotes: 0

Esteban E

Reputation: 65

I try this and works fine!

MAIN.cpp

#include <iostream>
#include "MathObject.h"
using namespace std;

int main(int args, char *argv[]){
    MathObject *mo = new MathObject(3,4);
    int sum = mo->sum();

    MathObject mo2(3,4);
    int sum2 = mo2.sum();

    cout << sum << endl;
    cout << sum2 << endl;
    system("pause");
    return 0;
}

MathObject.h

class MathObject
{
private:
    int num1;
    int num2;
public:
    MathObject(void);
    ~MathObject(void);
    int sum();
    MathObject(int n, int m);
};

MathObject.cpp

#include "MathObject.h"

MathObject::MathObject(void)
{
}

MathObject::~MathObject(void)
{
}
int MathObject::sum(){
    return num1+num2;
}
MathObject::MathObject(int n, int m){
    num1 = n;
    num2 = m;
}

Compile with: