Why my addText() function dont work?

[ElfMoon]

Why my addText() function dont work?
Here is code

/* Dialog Example */
#include "mainwindow.h"
#include <QApplication>
#include <QGridLayout>
#include <QLabel>
#include <QLineEdit>
#include <QMainWindow>
#include <QPushButton>
#include <QTextBrowser>
#include <QWidget>
class GUI : public QMainWindow {

       Q_OBJECT

       QWidget *window;
       QLineEdit *gui001;
       QTextBrowser *gui002;
       QTextBrowser *gui003;
       QTextBrowser *gui004;
       QTextBrowser *gui005;
       QTextBrowser *gui006;
       QTextBrowser *gui007;
       QTextBrowser *gui008;
       QTextBrowser *gui009;
       QTextBrowser *gui010;
       QTextBrowser *gui011;
       QPushButton *forward;

     public:
       GUI();
       virtual ~GUI();
       void addText();

     private:
};

GUI::GUI() {
       window = new QWidget();
       QGridLayout *layout = new QGridLayout;

       // Sukuriami procesų label'iai

       QLabel *startStopLabel = new QLabel( "Start_Stop" );
       QLabel *readUILabel = new QLabel( "ReadUI" );
       QLabel *jclLabel = new QLabel( "JCL" );
       QLabel *dataToOutputLabel = new QLabel( "DataToOutput" );
       QLabel *inputToRamLabel = new QLabel( "InputToRam" );
       QLabel *mainProcLabel = new QLabel( "MainProc" );
       QLabel *jobGovernorLabel = new QLabel( "JobGovernor" );
       QLabel *loaderLabel = new QLabel( "Loader" );
       QLabel *virtualMachineLabel = new QLabel( "VirtualMachine" );
       QLabel *interruptLabel = new QLabel( "Interrupt" );
       QLabel *printErrorLabel = new QLabel( "PrintError" );

       // Sukuriami procesų laukai duomenų išvedimui

       gui001 = new QLineEdit();
       QString qString01 = "GUI-001  QLineEdit 01";
       gui001->setText( qString01 );
       gui002 = new QTextBrowser();
       qString01 = "GUI-002  QTextBrowser 02";
       gui002->setText( qString01 );
       gui003 = new QTextBrowser();
       qString01 = "GUI-003  QTextBrowser 03";
       gui003->setText( qString01 );
       gui004 = new QTextBrowser();
       qString01 = "GUI-004  QTextBrowser 04";
       gui004->setText( qString01 );

       gui005 = new QTextBrowser();
       qString01 = "GUI-005  QTextBrowser 05";
       gui005->setText( qString01 );
       gui006 = new QTextBrowser();
       qString01 = "GUI-006  QTextBrowser 06";
       gui006->setText( qString01 );
       gui007 = new QTextBrowser();
       qString01 = "GUI-007  QTextBrowser 07";
       gui007->setText( qString01 );
       gui008 = new QTextBrowser();
       qString01 = "GUI-008  QTextBrowser 08";
       gui008->setText( qString01 );
       gui009 = new QTextBrowser();
       qString01 = "GUI-009  QTextBrowser 09";
       gui009->setText( qString01 );
       gui010 = new QTextBrowser();
       qString01 = "GUI-010  QTextBrowser 10";
       gui010->setText( qString01 );
       gui011 = new QTextBrowser();
       qString01 = "GUI-011  QTextBrowser 11";
       gui011->setText( qString01 );
       forward = new QPushButton( "Forward" );
       connect( forward, SIGNAL( clicked() ), this, SLOT( addText() ) );

       layout->addWidget( startStopLabel, 0, 0, Qt::AlignHCenter );
       layout->addWidget( readUILabel, 0, 1, Qt::AlignHCenter );
       layout->addWidget( jclLabel, 0, 2, Qt::AlignHCenter );
       layout->addWidget( dataToOutputLabel, 0, 3, Qt::AlignHCenter );
       layout->addWidget( gui001, 1, 0 );
       layout->addWidget( gui002, 1, 1 );
       layout->addWidget( gui003, 1, 2 );
       layout->addWidget( gui004, 1, 3 );
       layout->addWidget( inputToRamLabel, 2, 0, Qt::AlignHCenter );
       layout->addWidget( mainProcLabel, 2, 1, Qt::AlignHCenter );
       layout->addWidget( jobGovernorLabel, 2, 2, Qt::AlignHCenter );
       layout->addWidget( loaderLabel, 2, 3, Qt::AlignHCenter );
       layout->addWidget( gui005, 3, 0 );
       layout->addWidget( gui006, 3, 1 );
       layout->addWidget( gui007, 3, 2 );
       layout->addWidget( gui008, 3, 3 );
       layout->addWidget( virtualMachineLabel, 4, 0, Qt::AlignHCenter );
       layout->addWidget( interruptLabel, 4, 1, Qt::AlignHCenter );
       layout->addWidget( printErrorLabel, 4, 2, Qt::AlignHCenter );
       layout->addWidget( gui009, 5, 0 );
       layout->addWidget( gui010, 5, 1 );
       layout->addWidget( gui011, 5, 2 );
       layout->addWidget( forward, 5, 3 );

       window->setLayout( layout );
       window->setWindowState( Qt::WindowMaximized );
       window->setWindowTitle( "AutoMagic" );
       window->setWindowIcon( QIcon( "kiriya.jpg" ) );
       window->show();
}

GUI::~GUI() {}

void GUI::addText() {
       QString qString01 = "works";
       gui001->setText( qString01 );
       window->repaint();
}

int main( int argc, char *argv[] ) {
       QApplication app( argc, argv );
       GUI dialog;
       return app.exec();
}

#include "main.moc"

[jsulm]

@ElfMoon addText was not declared as slot. It needs to be:

public slots:
    void addText();

Please read https://doc.qt.io/qt-5/signalsandslots.html