Question

I encounter a problem using std::string in parameters :

MyClass has a method like this

public:  
    void loadDatas(string filename);

In my main.cpp I have the following simple code :

#include <iostream>
#include <string>

#include "myclass.hpp";

using namespace std;

int main()
{

    string foo = "test.txt";
    cout << foo << endl; // Print Hello Kitty, no problems

    MyClass i;
    // The following line raise :
    // obj/Release/src/main.o||In function `main':|
    // main.cpp|| undefined reference to `MyClass::loadDatas(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
    // ||=== Build finished: 1 errors, 0 warnings ===|
    i.loadDatas(foo);

    return EXIT_SUCCESS;

}

So it looks like libstdc++ is well linked (because I’m able to print the text using cout), but passing a string in parameters raise an error and I don’t understand why.

Could someone help me please ?

EDIT : I made a mistake, in fact it is i.loadDatas(foo); (I corrected it). My source code isn’t in english so I tryed to made a simple version for you in english. I really call an instance method and not a static method.

EDIT 2 : Complete source code

personnage.hpp

#ifndef PERSONNAGE_H
#define PERSONNAGE_H

#include <iostream>
#include <string>

#include <libxml/tree.h>
#include <libxml/parser.h>
#include <libxml/xmlmemory.h>
#include <libxml/xpath.h>
#include <libxml/xpathInternals.h>

#include "carte.hpp"

using namespace std;

class Personnage : public Carte
{

    public:

        Personnage();

        void chargerPersonnage(string nom);

        virtual ~Personnage();

    private:

        //! Le texte d'accroche de la carte
        string _accroche;

};

#endif // PERSONNAGE_H

personnage.cpp

#include "personnage.hpp"

Personnage::Personnage() : Carte("Sans titre")
{

}

void chargerPersonnage(string nom)
{

}

Personnage::~Personnage()
{
    //dtor
}

main.cpp

#include <iostream>
#include <string>

#include <SFML/Graphics.hpp>

#include "personnage.hpp"

using namespace sf;
using namespace std;

int main()
{

    string test = "Hello Kitty";
    cout << test << endl;

    Personnage test2;
    test2.chargerPersonnage(test);

    return EXIT_SUCCESS;
}

error log

obj/Release/src/main.o||In function `main':|
main.cpp|| undefined reference to `Personnage::chargerPersonnage(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
||=== Build finished: 1 errors, 0 warnings ===|

Answer 1

The problem is that you’ve defined class Personnage as having a member function chargerPersonnage, but in personnage.cpp you define a free function chargerPersonnage instead.

You appear to know the correct syntax, as you did Personnage‘s constructor and destructor correctly, but just to make it clear: Change void chargerPersonnage(string nom) { } to void Personnage::chargerPersonnage(string nom) { } in personnage.cpp.