Undefined reference to class::function in c++ - c++

Question

When I try to call OnLoop I get error that it doesn't recognise it.
///Ins_App.h
#ifndef INS_APP_H
#define INS_APP_H
#include <SDL/SDL.h>
class Ins_App
{
private:
/* Variables */
bool Running;
SDL_Surface* Surf_Display;
public:
/* inMain */
Ins_App();
int OnExecute();
public:
/* Other */
bool OnInit();
void OnEvent(SDL_Event* Event);
void OnLoop();
void OnRender();
void OnCleanup();
protected:
};
#endif // INS_APP_H
///Ins_App.cpp
#include "Ins_App.h"
Ins_App::Ins_App()
{
Running = true;
Surf_Display = NULL;
}
int Ins_App::OnExecute(){
if(OnInit() == false){
return -1;
}
SDL_Event Event;
while(Running){
while(SDL_PollEvent(&Event)){
OnEvent(&Event);
}
OnLoop();
OnRender();
}
return 0;
}
int main(int argc, char* argv[]){
Ins_App iApp;
return iApp.OnExecute();
}
///OnLoop.cpp
#include "Ins_App.h"
void OnLoop(){
}
And here is the error:
obj\Debug\src\Ins_App.o:C:\Users\Al\Documents\Ins
\src\Ins_App.cpp|19|undefined reference to `Ins_App::OnLoop()'|
What am I doing wrong?

Answer 1

You didn't define your member:
void OnLoop(){
}
should be
void Ins_App::OnLoop(){
}
You're basically just defining a free function named OnLoop, not your member.