The mainwindow header looks like:
Qt Code: 
  1. class MainWindow : public QMainWindow
  2. {
  3.     Q_OBJECT
  4.  
  5. public:
  6.     explicit MainWindow(QWidget *parent = 0);
  7.     bool eventFilter(QObject *obj, QEvent *event);
  8.     ~MainWindow();
  9.  
  10. private:
  11.     Ui::MainWindow *ui;
  12.     connection *con;
  13. };
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Mainwindow source looks like:


Qt Code: 
  1. MainWindow::MainWindow(QWidget *parent) :
  2.     QMainWindow(parent),
  3.     ui(new Ui::MainWindow)
  4. {
  5.     ui->setupUi(this);
  6.  
  7.     ui->lineEdit->installEventFilter(this);
  8.     QObjectList o_list = ui->lineEdit->children();
  9.     for(int i = 0; i < o_list.length(); i++)
  10.     {
  11.         QLineEdit *cast = qobject_cast<QLineEdit*>(o_list[i]);
  12.         if(cast)
  13.             cast->installEventFilter(this);
  14.     }
  15.  
  16. }
  17.  
  18.  
  19.  
  20. bool MainWindow::eventFilter(QObject *obj, QEvent *event)
  21. {
  22.     if(event->type() == QEvent::MouseButtonPress)
  23.     {
  24.       con->show();
  25.     }
  26.     return false;
  27. }
  28.  
  29.  
  30. MainWindow::~MainWindow()
  31. {
  32.     delete ui;
  33. }
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the Ui window contains a lineedit each.the connection window contains a textbox and the mainwindow contains another.The objective is to transfer the string/data from the widget window to main window using connect or any other method.