Unresolved external symbol signal

[A Former User]

I created an instance of QGuiApplication and a signal in order test if it works and I always get that the compiler could not resolve external symbols:

test.hpp:

#ifndef TEST_HPP
#define TEST_HPP

#include <QGuiApplication>

class test : public QGuiApplication
{

public:
  explicit test(int &argc, char **argv);

signals:
  void signalTest();
};

#endif // TEST_HPP

test.cpp:

#include "test.hpp"

test::test(int &argc, char **argv) : QGuiApplication(argc, argv)
{
  emit signalTest();
}

I tried to clean the build, remove the built files and build again, and nothing.

[mrjj]

add Q_OBJECT to your class
class test : public QGuiApplication
{
Q_OBJECT

and clean, and rebuild all

All classes that uses signals&slots must have this

[A Former User]

@mrjj That is weird, I tried and I got a lot of errors before, maybe because I needed to delete/clean first.
I thought that Q_OBJECT was only supposed to be used with QObject classes.

Thank you, it is solved.

[mrjj]

@Minupi
well the Q_OBJECT is used by the moc.exe compiler and sometimes its
a bit lazy it seems. so when anything else fails, i delete the build folder :)
Well, its need for the meta system used for signals.
But frankly I never tried to make a QApplication subclass but normally that the
case with all other subclassing.
Update: QApplication is a QCoreApplication which inherits from QObject

[A Former User]

@mrjj You are right about being a bit lazy. I need to delete the build folder as well sometimes, specially when creating a new class, for sure I will get errors and I need to delete the folder and build again.

[mrjj]

@Minupi
note. sometimes running qmake will also work.
It my understanding that "make file" calls moc.exe
But i have had cases where it would first like after I deleted build folder.
(regardless of clean/qmake/rebuild all)