Error LNK2019 while implementing a constructor - c++

Question

I am having some trouble with the implementation of a constructor and I cannot figure out what is the problem. I have spent a lot of time with this problem: it would be grateful some kind of advice.
The main code is:
#include "stdafx.h"
#include "Rocket.h"
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
Rocket* rocket;
rocket=new Rocket();
//LLA* position=rocket->positionLLA;
return 0;
}
Rocket.h
#pragma once
#include "LLA.h"
class Rocket {
public:
Rocket(); // Default constructor
LLA* positionLLA;
};
Rocket.cpp
#include "stdafx.h"
#include "Rocket.h"
#include <iostream>
using namespace std;
Rocket::Rocket() // Default constructor
{
// Initialise the position
positionLLA=new LLA();
}
The error says:
error LNK2019: unresolved external symbol "public: __thiscall Rocket::Rocket(void)" (??0Rocket##QAE#XZ) referenced in function _main.
I know the error has something to do with not having declared a variable, but I think I have declared all classes and constructors.
PS: I am using Visual Studio 2008 in order to add dependencies.

Answer 1

I am assuming LLA is correctly defined in your .h file
Are you compiling Rocket.cpp into Rocket.o and main.cpp into main.o and then linking the two object files together?
Your error seems to imply that the linker cannot obtain symbol information from Rocket.o, which usually means Rocket.o was not found
Oh, as a detail, since Rocket is using an LLA*, you don't need to include LLA.h in Rocket.h, you can simply forward-declare
class LLA;

Answer 2

You might want to add #ifndef, #define, and #endif to your header files. Having multiple includes of the same thing in different files can lead to complications.