Qt C++ - Can't add slots - c++

Question

When I add slots to my script it will no longer build.
inkpuppet.obj:-1: error: LNK2005: "private: void __cdecl InkPuppet::on_aboutButton_clicked(void)" (?on_aboutButton_clicked#InkPuppet##AEAAXXZ) already defined in main.obj
and
debug\InkPuppet.exe:-1: error: LNK1169: one or more multiply defined symbols found
Here is the code:
inkpuppet.h - commenting out void on_aboutButton_clicked(); and the function at the end will make it run.
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
#include <QtCore>
namespace Ui {
class InkPuppet;
}
class InkPuppet : public QWidget
{
Q_OBJECT
public:
explicit InkPuppet(QWidget *parent = 0);
~InkPuppet();
private:
Ui::InkPuppet *ui;
private slots:
void on_aboutButton_clicked();
};
#endif // WIDGET_H
void InkPuppet::on_aboutButton_clicked()
{
}
inkpuppet.cpp
#include "inkpuppet.h"
#include "ui_inkpuppet.h"
InkPuppet::InkPuppet(QWidget *parent) :
QWidget(parent),
ui(new Ui::InkPuppet)
{
ui->setupUi(this);
//connect(ui->lowerFrameBox, SIGNAL(valueChanged(int)), ui->timeSlider, SLOT(setRange(int,int)));
}
InkPuppet::~InkPuppet()
{
delete ui;
}
main.cpp
#include "inkpuppet.h"
#include "aboutdialog.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
InkPuppet w;
w.show();
return a.exec();
}
aboutdialog.h
#ifndef ABOUTDIALOG_H
#define ABOUTDIALOG_H
#include <QDialog>
namespace Ui {
class AboutDialog;
}
class AboutDialog : public QDialog
{
Q_OBJECT
public:
explicit AboutDialog(QWidget *parent = 0);
~AboutDialog();
private:
Ui::AboutDialog *ui;
};
#endif // ABOUTDIALOG_H
aboutdialog.cpp
#include "aboutdialog.h"
#include "ui_aboutdialog.h"
AboutDialog::AboutDialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::AboutDialog)
{
ui->setupUi(this);
}
AboutDialog::~AboutDialog()
{
delete ui;
}

Answer 1

You define your void InkPuppet::on_aboutButton_clicked() in your inkpuppet.h. And then you include it in inkpuppet.cpp AND in main.cpp -> one or more multiply defined symbols found.
Put
void InkPuppet::on_aboutButton_clicked()
{
}
in your inkpuppet.cpp file.

Answer 2

If the first file you pasted is a whole, there's a problem with the include guards. The definition is after the guard's end.
#endif // WIDGET_H
void InkPuppet::on_aboutButton_clicked()
{
}
Your definition is right after the #endif which means as soon as in the same translation unit, the header is included twice, you'll get this error. And this happens in your code because inkpuppet.h is included in both main.cpp and in inkpuppet.cpp You should put the implementation code for on_aboutButton_clicked() in your inkpuppet.cpp file.