(epics)QT compilation error: "undefined reference to" - qt

Question

I am brand new to programming with Qt. I'm trying to do a simple subtraction of some values fed from an epicsQt widget called QELabel, which simply reads the value of an EPICS channel. I want to subtract values from two QELabels and print it to another QELabel. But, I'm getting 'undefined reference to' errors for these ->
MainWindow::on_qeLabel_dbValueChanged(QString const&) MainWindow::on_ShutterOpen_dbValueChanged(QString const&)
Here is the bit of mainwindow.cpp (I followed the example from this youtube video, especially after about the 15 minute mark)
void MainWindow::on_TopShutter_dbValueChanged(const QString &out)
{
double top,bottom,open;
top=ui->TopShutter->text().toDouble();
bottom=ui->BottomShutter->text().toDouble();
open=top-bottom
ui->ShutterOpen->setText(Qstring::number(open));
}
I'm using QTCreator, so I don't have the usual errors that I've been seeing in other forums. I have the slot declared in the header file, and MainWindow set as a Q_Object (this is the whole mainwindow.h file):
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_qelabel_dbValueChanged(const QString &out);
void on_ShutterOpen_dbValueChanged(const QString &out);
void on_TopShutter_dbValueChanged(const QString &out);
private:
Ui::MainWindow *ui;
};
#endif //MAINWINDOW_H
Because they are short, and for completeness, here is the main.cpp, and then the .pro
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
And the FirstWeatherAlarm.pro:
#-------------------------------------------------
QT += core gui xml
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = FirstWeatherAlarm
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
LIBS += -L/usr/lib64/qt5/plugins/designer -lQEPlugin
INCLUDEPATH += /home/jchavez/epicsqt/3.1.0/framework/include
HEADERS += mainwindow.h
FORMS += mainwindow.ui
Have I got everything declared right at the start of all the files? What is missing so that my slots are not right? I created the slot in the gui, using the "right-click" on my QELabel, and selecting "Go to Slot", so I should think all the formatting would be correct. As I've been editing, I've also run qmake and make clean which are other answers I've seen on forums. But nothing is working.

Answer 1

The problem is with two slots:
MainWindow::on_qeLabel_dbValueChanged(QString const&)
MainWindow::on_ShutterOpen_dbValueChanged(QString const&)
They are declared in MainWindow.h file and used somewhere in your project (otherwise you won't get an error).
But they are not implemented in mainwindow.cpp. You should add implementation to this file and the error will go away.
You have implementation for
void MainWindow::on_TopShutter_dbValueChanged(const QString &out)
in mainwindow.cpp, you can add implementation for two more slots. Think about slot as a function. And read more about signals/slots.