Question

I’m using VisualStudio 2010 to build a simple program with Qt 4.8.3, and i’m having trouble with a simple method definition:

here is my code:

GuiHelper.h

#ifndef GUIHELPER_H 
#define GUIHELPER_H

#include "GuiHelper.cpp"
#include <QString>
#include <QWidget>
#include <QFile>

class GuiHelper
{
private:
static void useStyleSheet(QString, QWidget*);  
};
#endif //GUIHELPER_H

and GuiHelper.cpp:

#include <QString>
#include <QWidget>
#include <QFile>
#include "GuiHelper.h"

void GuiHelper::useStyleSheet(QString filename, QWidget* widget)
{
// loads style file and apply style
QFile file(":/Resources/"+filename);
file.open(QFile::ReadOnly);
QString styleSheet = QLatin1String(file.readAll());
widget->setStyleSheet(styleSheet);
}

I get the error C2653: GuiHelper is not a class or a namspace but I don’t really see what’s wrong…

I also checked “no precompiled headers” when creating the project with the QT addin

thanks!

Answer 1

Quickfix – remove the

#include "GuiHelper.cpp"

from the header.

Cause of the problem: the compiler compiles the sources – that is the .cpp files. It starts parsing the cpp file and reaches

#include "GuiHelper.h"

which tells it to process the header and paste its contents – the second line of the header does

#define GUIHELPER_H

Afterwards, you

#include "GuiHelper.cpp"

which in turn attempts to process and paste the cpp file, which again tries to process the header. Because GUIHELPER_H was already defined, the header is no longer processed, but remember that the class was not yet defined. So it gets to the line

void GuiHelper::useStyleSheet(QString filename, QWidget* widget)

but you get the error because GuiHelper was not defined yet.