tbscope , i checked that but i didn't initialise any of the UI items manually.i left what uic generated . Is that necessary to initialise them ?

here's the code ....they're simple .
mainwindow.h

Qt Code: 
  1. #ifndef MAINWINDOW_H
  2. #define MAINWINDOW_H
  3. #include <QMainWindow>
  4. #include <QMessageBox>
  5. #include "ui_mainwindow.h"
  6.  
  7. namespace Ui {
  8.     class MainWindow;
  9.     class Ui_MainWindow;
  10. }
  11.  
  12. class MainWindow : public QMainWindow ,public Ui_MainWindow
  13. {
  14.     Q_OBJECT
  15. public:
  16.     QString user;
  17.     QString pass;
  19.     explicit MainWindow(QWidget *parent = 0);
  20.     ~MainWindow();
  21. private:
  22.     Ui::MainWindow *ui;
  23. private slots:
  24.     void on_login_clicked();
  25. };
  26. #endif // MAINWINDOW_H
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mainwindow.cpp

Qt Code: 
  1. #include "mainwindow.h"
  2. #include "ui_mainwindow.h"
  3.  
  4. MainWindow::MainWindow(QWidget *parent) :
  5.     QMainWindow(parent),
  6.     ui(new Ui::MainWindow)
  7. {
  8.     ui->setupUi(this);
  9. }
  10. MainWindow::~MainWindow()
  11. {
  12.     delete ui;
  13. }
  14. void MainWindow::on_login_clicked()
  15. {
  16. user=usernameip->displayText();
  17. pass=passwordip->displayText();
  18.     if(user.compare("user")&&pass.compare("pass"))
  19.     {
  20.         //msg.setText("The username is correct");
  21.         //msg.exec();
  22.     }
  23. }
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And the uic generated file ui_mainwindow.h file
Does anyone has idea wat's wrong ?