QString methods causing undefined reference to errors

Question

#include <QCoreApplication>
#include <vector>
#include <string>
#include <vector>
#include <QString>
#include <QVector>
#include <Method.h>

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

    QVector< QString> vec;

    QVector< QVector < QString> > mat;

    vector<string> vect;

    vector<vector<string> > matr;




    vec = Method::bogus(vect);

    mat = Method::bogusMa(matr);

}

#include <vector>
#include <string>
#include <vector>
#include <QString>
#include <QVector>
#include <Method.h>

using namespace::std;

QVector<QString> bogus(vector<string> & vec)
{
    QVector< QString > result;


    return result;

}

QVector<QVector <QString> > bogusMa(vector<vector<string> > & vec)
{

    QVector< QVector<QString> > result;


    return result;

}


#ifndef METHOD_H
#define METHOD_H

#include <vector>
#include <string>
#include <vector>
#include <QString>
#include <QVector>
#include <Method.h>

using namespace::std;

class Method{


public:
    static QVector<QString> bogus(vector<string> & vec);
    static QVector<QVector <QString> > bogusMa(vector<vector<string> > & vec);

};

#endif // METHOD_H

This is weird, because I don't get any error message when I am returning vectors containing anything else than QString. Sorry, if this sound like a dumb question, but I can't figure out exactly why I am getting this error. Does it have something to do with the include namespace statement in the header file? I don't see how those two might be connected. If it is the case, can you explain why it gives me an error?

Before we can help you, this error != NULL must be TRUE. — MrDuk
– MrDuk, Commented Apr 4, 2014 at 2:46
Just that there's no reference to what you mean by "this error" — MrDuk
– MrDuk, Commented Apr 4, 2014 at 12:35

gan_ · Accepted Answer · 2014-04-04 04:09:36Z

1

When implementing a method, you need to specify the class there are in

QVector<QString> bogus(vector<string> & vec)

become

QVector<QString> Method::bogus(vector<string> & vec)

And

QVector<QVector <QString> > bogusMa(vector<vector<string> > & vec)

become

QVector<QVector <QString> > Method::bogusMa(vector<vector<string> > & vec)

The prototype for the method must also be included BEFORE its implementation, so you should move these after your class declaration.

answered Apr 4, 2014 at 4:09

gan_

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2 Comments

user3435009 Over a year ago

what if they are not in the same file (I have a header and a cpp file)?

gan_ Over a year ago

In that case you need to include the header in the cpp file, and in the main (the "Method::" are still necessary in the cpp)

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