After adding Q_OBJECT , getting compile error

[Aminul]

Hello, here is my header file of a very simple class.

#ifndef MYTHREAD_H
#define MYTHREAD_H

#include <QObject>
#include <QThread>

class MyThread : public QThread
{

Q_OBJECT

public:
MyThread();
void run();

signals:
void sending();
};

#endif // MYTHREAD_H

I have corresponding CPP file. When I compile this project I am getting below error.

g++ -m64 -o TestThread4 main.o mainwindow.o mythread.o moc_mainwindow.o -L/usr/lib/x86_64-linux-gnu -lQtGui -lQtCore -lpthread
mythread.o: In function MyThread::MyThread()': /home/aminul/build-TestThread4-Qt_4_8_7_in_PATH_qt5-**Debug/../TestThread4/mythread.cpp:4: undefined reference to vtable for MyThread'
Makefile:107: recipe for target 'TestThread4' failed**

This file comiles fine, if I remove "Q_OBJECT" the project complies fine.

What is the reason of this?

[aha_1980]

@Aminul it's a linker error.

You need to re-run qmake, then build again.

If that doesn't help, last resort is to delete the build folder and then build again.

[GuYan]

You have build the project before you add the Q_OBJECT. You can try to make some changes in the *.pro file such as add a space at the bottom. Then re-build it, usually it will solve this problem.