The problem:
Replace naked pointers with smart QPointers and use them with forward declared classes.
Background:
As advised by virtually all texts on modern C++, one should refrain from using naked pointers and use smart pointers instead. In the Qt toolkit there is a set of smart pointers available, with one of particular interest to me in this case: QWeakPointer (Qt 4) or QPointer (Qt 5), which is supposedly freely interchangeable with a naked pointer and is set to NULL when the respective object (derived from QObject) is deleted, thus helping prevent the all too common dangling pointer problem. Yet the requirement that the object pointed to by the QPointer be of a QObject-derived type prevents usage of forward declared classes.
The question: How do I combine QPointer-type variables with forward declared classes in the class header with forward declared types?
or
How do I avoid including the whole header file for an object for which I want to use the QPointer?
Example:
#pragma once
#include <QObject>
#include <QPointer>
class MyQWidget; // Forward-declared class
class SomeClass {
QPointer<MyQWidget> m_myWidget;
};
Note: I've read through wuestion like this one: In C++, is it possible to forward declare a class as inheriting from another class?. In my question, I'm looking for Qt-specific ways to overcome this limitation (or better design feature), if there are any.
Edit: My main compiler is MSVC 2010 and the error I get is
error C2079: 'MainWindow::m_test' uses undefined class 'QPointer<T>'
with
[
T=MyQWidget
]
