QtCreator part 3 tutorial
In the section titled Creating the Scene and View the user is instructed to add a forward declaration for:
class Scene;then to create a private variable to store a pointer to the scene:
private: Scene* m_scene;With the header file originally looking like this:
- #ifndef MAINWINDOW_H
- #define MAINWINDOW_H
- #include <QtGui/QMainWindow>
- /*************************************************************************************/
- /*********************** Main application window for QSimulate ***********************/
- /*************************************************************************************/
- {
- public:
- MainWindow(); // constructor
- };
- #endif // MAINWINDOW_H
where in the world is one supposed to place:
- class Scene;
- private:
- Scene* m_scene; // scene representing the simulated landscape
I’ve tried several locations – none of which make the compiler happy.
Thx!
2 replies
Actually, I think I just got it:
It really would have helped if, in the tutorial, it spelled out “add the new class declaration before the MainWindow class, then add the private variable declaration to the MainWindow class”.
- #ifndef MAINWINDOW_H
- #define MAINWINDOW_H
- #include <QtGui/QMainWindow>
- /*************************************************************************************/
- /*********************** Main application window for QSimulate ***********************/
- /*************************************************************************************/
- class Scene;
- {
- public:
- MainWindow(); // constructor
- private:
- Scene* m_scene; // scene representing the simulated landscape
- };
- #endif // MAINWINDOW_H
I guess it is assumed the very basics of C++ are known, in this case how forward-declaration works and what it’s good for.
If you’re new to (C++)programming, I tend to discourage starting with Qt right away. While Qt is a great role model for clean programming/naming/API design (I myself have learned a lot from the Qt wizards), it uses some quite tricky mechanisms that are way over the head of new programmers, and may distract from actually learning C++ (Meta object RTTI/MOC, qmake, Signals&Slots, pimpl, the whole event loop system, the different ways of memory management).
The STL is more down to earth regarding those things. And as a bonus, after learning to walk with C++ and STL a little, you’ll appreciate Qt much more and feel like flying.
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