Hi,
I'm trying to compile this code
Qt Code: 
  1. #include <QApplication>
  2. #include <QLCDNumber>
  3. #include <QPushButton>
  4. #include <QVBoxLayout>
  5. #include <QWidget>
  6.  
  7. class LCDCounter : public QLCDNumber{
  8. 	Q_OBJECT
  9.  
  10. private:
  11. 		int counter;
  12. public:
  13. 	LCDCounter(QWidget *parent = 0);
  14. public slots:
  15. 	void increase(void);
  16.  
  17. };
  18.  
  19. LCDCounter::LCDCounter(QWidget *parent)
  20. : QLCDNumber(parent)
  21. {
  22. 	counter = 0;
  23. 	setSegmentStyle(QLCDNumber::Filled);
  24. 	display(0);
  25. }
  26.  
  27. void LCDCounter::increase(){
  28. 	display(counter++);
  29. }
  30.  
  31. class MyWidget : public QWidget
  32.  {
  33. 	QPushButton *clickMe;
  34. 	LCDCounter *counter;
  35.  
  36.  public:
  37.      MyWidget(QWidget *parent = 0);
  38.  };
  39.  
  40.  MyWidget::MyWidget(QWidget *parent)
  41.      : QWidget(parent)
  42.  {
  43. 	 clickMe = new QPushButton("Click me!");
  44. 	 counter = new LCDCounter();
  45. 	 connect(clickMe,SIGNAL(clicked()),counter,SLOT(increase()));
  46.  
  47. 	 QVBoxLayout *boxLayout = new QVBoxLayout;
  48. 	 boxLayout->addWidget(clickMe);
  49. 	 boxLayout->addWidget(counter);
  50. 	 setLayout(boxLayout);
  51.  
  52.  }
  53.  
  54. int main(int argc, char *argv[])
  55. {
  56. 	QApplication a(argc, argv);
  57. 	MyWidget w;
  58. 	w.show();
  59. 	return a.exec();
  60. }
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But this error is returned.
Qt Code: 
  1. 1>main.obj : error LNK2001: sÃ*mbolo externo "public: virtual struct QMetaObject const * __thiscall LCDCounter::metaObject(void)const " (?metaObject@LCDCounter@@UBEPBUQMetaObject@@XZ) unresolved
  2. 1>main.obj : error LNK2001: sÃ*mbolo externo "public: virtual void * __thiscall LCDCounter::qt_metacast(char const *)" (?qt_metacast@LCDCounter@@UAEPAXPBD@Z) unresolved
  3. 1>main.obj : error LNK2001: sÃ*mbolo externo "public: virtual int __thiscall LCDCounter::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@LCDCounter@@UAEHW4Call@QMetaObject@@HPAPAX@Z) unresolved
  4. 1>C:\Users\ferran\directo\QT_Tutorials\Debug\Tutorial02.exe : fatal error LNK1120: 3 externos sin resolver
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How do I guess the method that fails? What are happening?

Many thanks in advance.