Undefined reference to class::method [duplicate] - c++

Question

This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 8 years ago.
In these days I thought I would try to work on some C++ Object Oriented Programming by converting one of my old programs to an object which methods I could use in other programs.
The program is able to get an array of strings and print them to make a selection screen like this:
"> Stuff"
" Stuff2"
" Stuff3"
And the cursor could then be moved with the keyboard arrows and one entry could be selected by pressing Enter.
Unfortunately, after having removed most errors the only left is a "Undefined reference to class::method()" for each method that I wrote.
The code is the following:
Selection.cpp
#include "selection.h"
#include <iostream>
#include <conio.h>
#include <stdio.h>
#include <cstring>
#include <string>
#include <vector>
std::vector<entry> selectedArray;
int posizione = 1, tastoPremuto;
void setCurrentArray(std::string selectionEntries[])
{
//Copies a string array to a vector of struct entry
}
void resetSelection()
{
//Blanks out every entry.segno
}
void selectionUpdate(int stato)
{
//Moves the cursor
}
int getPosition()
{
return posizione; //Returns the position of the cursor
}
void setPosition(int nuovaPosizione) //Sposta il puntatore alla nuovaPosizione
{
posizione = nuovaPosizione; //Sets the posiion of the cursor
}
entry getCurrentEntry(int posizioneCorrente) //Returna l'entry della posizione attuale
{
//Gets the name of the entry at which the cursor is
}
void printEntries() //Stampa tutte le entries con la selezione
{
//Prints all the entries with the cursor before them
}
int getSelection(bool needConfirm)
{
//gets the selection from keyboard
}
Selection.h
#ifndef SELECTION_H
#define SELECTION_H
#include <string>
#include <vector>
struct entry
{
std::string entryName;
char sign;
};
class selection
{
public:
selection();
virtual ~selection();
void setCurrentArray(std::string selectionEntries[]);
void resetSelection();
int getPosition();
void setPosition(int nuovaPosizione);
entry getCurrentEntry(int posizioneCorrente);
void printEntries(int argumentsNumber);
int getSelection(bool needConfirm);
protected:
private:
int tastoPremuto;
int posizione;
void selectionUpdate(bool stato);
std::vector<entry> selectedArray;
};
#endif // SELECTION_H
main.cpp
#include <stdio.h>
#include <iostream>
#include <conio.h>
#include <selection.h>
#include <vector>
#include <array>
std::string selezioneTestArray[3] = {"Prima selezione", "Seconda selezione", "Terza seleazione"};
int main()
{
selection sel;
sel.setCurrentArray(selezioneTestArray);
sel.setPosition(0);
sel.resetSelection();
sel.printEntries(3);
sel.getSelection(true);
return 0;
}
If you need the whole code, it's in my Github: https://github.com/LiceoFederici2H/Vita-Da-Lavoratore
Sorry if it's in Italian but I meant to use this also as a school project.
Thanks in advance.

Answer 1

In source file (Selection.cpp), you have to qualify the method names with class name:
void Selection::setCurrentArray(std::string selectionEntries[])
{
//Copies a string array to a vector of struct entry
}
Otherwise these methods will be free function, and not definition of the class methods. As a result, your class methods remain undefined, and when linker tries to link with the methods, it can not find them, and shows undefined reference of the method error.