Why am I getting a 'not a signal declaration' error in this header file?

DragonautX

I'm reading about "Signals & Slots" from the docs, and I wanted to try a test class. In a "header.h", I made a subclass of QPushButton called PushButtonWIdget, and made one slot, one signal, and one function to call the signal. However, on building it, I get an error in my signalFunction definition saying "Not a signal declaration". Why did I get this error? I'm pretty sure I can define signal functions with qDebug for example since they're just like any other function.

#ifndef HEADER_H
#define HEADER_H

#include <QPushButton>
#include <QDebug> //edit: added this too, since << syntax returns type QDebug

class PushButtonWidget: public QPushButton {
    Q_OBJECT
public:
    void callSignal() {
        emit signalFunction();
    }
public slots:
    void slotFunction() {
        qDebug() << "The slot slotFunction was called.";
    }
signals:
    void signalFunction() {
        qDebug() << "The signal signalFunction was called";
    }
};



#endif // HEADER_H

VRonin

signals are implemented by moc you can't provide a body for them

signals:
    void signalFunction();

P.S.
You are currently breaking the parent child mechanism as well, you should add a constructor like this one:

public:
explicit PushButtonWidget(QWidget* parent = NULL)
:QPushButton (parent)
{
// I also suppose you want to link the signal and slot together? maybe?
connect(this,&PushButtonWidget::signalFunction,this,&PushButtonWidget::slotFunction);
}

@DragonautX said in Why am I getting a 'not a signal declaration' error in this header file?:

I'm pretty sure I can define signal functions with qDebug

You can declare but not define. The qDebug part I did not get

DragonautX

Oh, that's why. Thanks, also for the mechanism fix and the connect() tip. I was going to connect via making two PushButtonWidget instances and using QObject::connect() in my "main.cpp", but using connect in the constructor is a nice idea too.

Sorry, I meant if I could add a definition for my signal function, I thought I could add lines like qDebug() in the function block like I can for any function definition. I thought including the line qDebug in the function block was causing the problem, but I see it was actually defining the signal itself that was the problem.