初始qt，第一个编译错误

#include <qapplication.h>
#include <qwidget.h>
#include <qslider.h>
#include <qprogressbar.h>
#include <qpushbutton.h>

class MyMainWindow : public QWidget
{
Q_OBJECT
        public:
                MyMainWindow();
                public slots:
                        void set_step();
        private:
                QProgressBar *bar;
                //      QSlider *slider;
                QPushButton *add;
                QPushButton *dec;
};

MyMainWindow::MyMainWindow()
{
        setGeometry(100, 100, 200, 90);

        bar = new QProgressBar(100, this);
        bar->setGeometry(10, 10, 180, 30);

        add = new QPushButton("+", this);
        add->setGeometry(10, 50, 10, 10);
        dec = new QPushButton("-", this);
        dec->setGeometry(50, 50, 10, 10);

//              slider = new QSlider(0, 100, 10, 0, Horizontal, this);
//              slider->setGeometry(10, 50, 180, 30);

        connect(add, SIGNAL(clicked()), this , SLOT(set_step()));
        connect(dec, SIGNAL(clicked()), this , SLOT(set_step()));
}

void MyMainWindow::set_step()
{
        printf("haha");
}

int main(int argc, char **argv)
{
        QApplication a(argc, argv);
        MyMainWindow w;
        a.setMainWidget(&w);
        w.show();
        a.exec();
} 

编译报出：

progress.o: In function `MyMainWindow::MyMainWindow()':
progress.cpp:(.text+0x1dc): undefined reference to `vtable for MyMainWindow'
progress.o: In function `main':
progress.cpp:(.text+0x268): undefined reference to `vtable for MyMainWindow'
progress.o: In function `MyMainWindow::MyMainWindow()':
progress.cpp:(.text+0x43c): undefined reference to `vtable for MyMainWindow'

我的解决办法，把类定义包含到头文件中去

 原因：qmake不会处理.cpp文件里的Q_OBJECT,所以,如果在.cpp文件中有它的话,也会产生undefined reference to vtable for "xxx::xxx". 这时,需要先用moc xxxx.cpp生成相应的moc文件,再包含到.cpp里面去,才能解决这个问题.

引用来源：http://blog.donews.com/netexe/archive/2006/02/09/720544.aspx