[Qt-interest] Optionally deriving from QWidget

[David Doria]

I have a class that emits Qt signals. I want to use this class in two ways:

1) Interactive - I want to use this class as part of a Qt GUI application
that can handle the signals.
2) Non-interactive - I want to use this class in a command line application
that does not know about Qt.

I tried defining a compiler flag INTERACTIVE and then doing something like
this:

#ifndef FORM_H
#define FORM_H

#if defined(INTERACTIVE)
#warning "Using interactive!"
#include <QWidget>
class Form : public QWidget
#else
#warning "Not using interactive!"
class Form
#endif
{
  #if defined(INTERACTIVE)
    Q_OBJECT

public:


  public slots:

  #endif
};

#endif

but even when the flag is defined, I get some vtable errors.

CMakeFiles/interactive.dir/interactive.cpp.o: In function `Form':
/media/portable/Examples/c++/src/QT/OptionalQt/form.h:14: undefined
reference to `vtable for Form'
/media/portable/Examples/c++/src/QT/OptionalQt/form.h:14: undefined
reference to `vtable for Form'
CMakeFiles/interactive.dir/interactive.cpp.o: In function `~Form':
/media/portable/Examples/c++/src/QT/OptionalQt/form.h:14: undefined
reference to `vtable for Form'
/media/portable/Examples/c++/src/QT/OptionalQt/form.h:14: undefined
reference to `vtable for Form'

Is this the right way to go about this? Can anyone explain where I went
wrong?

Thanks,

David
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