C++ error: Invalid use of incomplete type …

Question

I have a small- to medium-size project that I am doing for my software engineering course this semester. I have chosen to do it in C++ (gtkmm). I am doing okay so far but I

Answer 1

You can get away with forward declaring MainWindow in Login_Dialog.h as long as you only forward declar a pointer to the type (which you do), and you add this to the top of Login_Dialog.h so the compiler knows to expect to see a class declaration at some later time.

class MainWindow;

Then in Login_Dialog.cpp, include "mainwindow.h" like this.

/*
 * Login_Dialog.cpp
 *
 *  Created on: Mar 2, 2010
 *      Author: Matthew
 */

#include "Login_Dialog.h"
#include "MainWindow.h"

That should do it.