error opening a new dialog on button click

[prkhr4u]

I am trying to open a new dialog from a button click inside the mainwindow.
My code is as follows:

void MainWindow::on_btn_login_clicked()
{
if (count == 1)
        {                      
                dialog->show();
                dialog->raise();
                dialog->activateWindow(); 
        }
}

void MainWindow::on_btn_login_clicked()
{
if (count == 1)
        {                      
                dialog->show();
                dialog->raise();
                dialog->activateWindow(); 
        }
}

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My Mainwindow .h is as follows:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include "dialog.h"
namespace Ui {
class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
private slots:
    void on_btn_magnifier_clicked();
 
    void on_btn_login_clicked();
private:
    Ui::MainWindow *ui;
    Dialog *dialog;
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "dialog.h"
namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT
    
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    
private slots:
    void on_btn_magnifier_clicked();

    void on_btn_login_clicked();
private:
    Ui::MainWindow *ui;
    Dialog *dialog;
};

#endif // MAINWINDOW_H

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I have made a new form named dialog.ui with dialog.cpp and dialog.h
When i am debugging the application,segmentation fault is coming on the line:

dialog->show();

dialog->show();

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[Lesiok]

Pointer dialog is not initialized.

[prkhr4u]

Thank you.
added this to btn_login_clicked:

Dialog *dialog=new Dialog();

Dialog *dialog=new Dialog();

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Now everything working and i am able to open a new window on the button click