simple problem for your guys

i'm getting the following errors when i run this simple program...the application is supposed to close if the user types "nice" in the LineEdit and clicks the quit button, i'm also very new to Qt...i have a huge proj coming up due in April. Can you guys help me?

nice error LNK2001: unresolved external symbol "public: virtual bool __thiscall Checker::qt_emit(int,struct QUObject *)" (?qt_emit@Checker@@UAE_NHPAUQUObject@@@Z)
nice error LNK2001: unresolved external symbol "public: virtual bool __thiscall Checker::qt_invoke(int,struct QUObject *)" (?qt_invoke@Checker@@UAE_NHPAUQUObject@@@Z)
nice error LNK2001: unresolved external symbol "public: virtual bool __thiscall Checker::qt_property(int,int,class QVariant *)" (?qt_property@Checker@@UAE_NHHPAVQVariant@@@Z)
nice error LNK2001: unresolved external symbol "public: virtual char const * __thiscall Checker::className(void)const " (?className@Checker@@UBEPBDXZ)
nice error LNK2001: unresolved external symbol "public: virtual void * __thiscall Checker::qt_cast(char const *)" (?qt_cast@Checker@@UAEPAXPBD@Z)
nice error LNK2019: unresolved external symbol "public: static class QMetaObject * __cdecl Checker::staticMetaObject(void)" (?staticMetaObject@Checker@@SAPAVQMetaObject@@XZ) referenced in function "public: virtual class QMetaObject * __thiscall Checker::metaObject(void)const " (?metaObject@Checker@@UBEPAVQMetaObject@@XZ)
nice fatal error LNK1120: 6 unresolved externals

HERE IS THE CODE:

#include
#include
#include
#include

class Checker : public QObject
{
Q_OBJECT
public slots:

void on_text_Change ( const QString& str )
{
if (str == "nice")//allow_quit = ( str == "nice" );
allow_quit = true;
}
void on_button_click()
{
if ( allow_quit )
quit();
}

signals:
void quit();
private:
bool allow_quit;
};

int main( int argc, char **argv )
{
QApplication a( argc, argv );

QPushButton *quit = new QPushButton( "Quit", 0, "quit" );

QLineEdit *line = new QLineEdit( QString("nice"),0,0 );

Checker chk;
QObject::connect( line, SIGNAL(textChanged(const QString&)), &chk, SLOT(on_text_Change(const QString&)) );
QObject::connect( quit, SIGNAL(clicked()), &chk, SLOT(on_button_click()) );
QObject::connect( &chk, SIGNAL(quit()), &a, SLOT(quit()) );

a.setMainWidget( line );
(*line).show();
(*quit).show();
return a.exec();
}