Cannot access methods of *ui widgets in defaultCodeModel

I disable clangCodeModel Plugin and use defaultCodeModel for autoComplete.
when i want to access widgets that sit in my ui file(for example: a pushbutton) autocomplete won't work properly.for example:

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent), ui(new Ui::MainWindow)

when i type ui and "." and press CTRL+SPACE from keyboard, qtCreator converto "." to ">" and offer me pushButton, but when i press "." ide nor convert it to ">" and show any member function of pushButton like "setText()";