Question

i have a full static class, using a std::map

thats the simplified case

.h

#ifndef KEYBOARD_H
#define KEYBOARD_H

#include <map>

class Keyboad {

    static std::map<char, bool> pressed;    

    static void keyPressedEvent(char _key); 

};

#endif

.cpp

#include "Keyboard.h"

void Keyboard :: keyPressedEvent(char _key) {

    Keyboard :: pressed[_key] = true;

}

but there is a problem with the static member variable, because i get

Undefined symbols:
"Keyboard::pressed", referenced from:
__ZN15Keyboard7pressedE$non_lazy_ptr in Keyboard.o
(maybe you meant: __ZN15Keyboard7pressedE$non_lazy_ptr)
ld: symbol(s) not found
collect2: ld returned 1 exit status

when i remove it, it runs ok

why do i get this problem, there should be no problem when using a static variable :/

thanks

Answer 1

You need to define the pressed map in your .cpp file:

#include "Keyboard.h"
std::map<char, bool> Keyboard::pressed;

// The rest as before