Qt5: error: ‘qt_metacall’ is not a member of

Question

I try to become more familiar with singnals and slots with Qt. I want to emit a signal in one class and want to handle it at one other. Here my example code:

main.c

#include "mainwindow.h" #include <QApplication> int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; w.show(); return a.exec(); }

mainwindow.h

#ifndef MAINWINDOW_H #define MAINWINDOW_H #include <QMainWindow> class Emiter { signals: void anSignal (); }; class MainWindow : public QMainWindow { Q_OBJECT private slots: void handleEmitter (); public: MainWindow(QWidget *parent = 0); }; #endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h" MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) { auto emiter = new Emiter(); connect( emiter, &Emiter::anSignal, this, &MainWindow::handleEmitter ); } void MainWindow::handleEmitter() { }

Then I get this error:

error: ‘qt_metacall’ is not a member of ‘Emiter’ enum { Value = sizeof(test(&Object::qt_metacall)) == sizeof(int) };

What does this mean?

Alex44 · Accepted Answer · 2018-02-02 12:36:03Z

Signals and slots are available only in QObject derived classes, and a Q_OBJECT macro is needed.

class Emiter : public QObject { Q_OBJECT public: signals: void anSignal (); };

For more detail answer: click here

W.Perrin · Accepted Answer · 2022-09-20 10:46:01Z

Another case is if you use multiple inheritances, you need to put QObject as the first parent class.

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