######################################################################
header file:
######################################################################

#ifndef GOTOCELLDIALOG_H
#define GOTOCELLDIALOG_H
#include <QDialog>
#include <QLineEdit>



class GoToCellDialog : public QDialog
{
    Q_OBJECT
private:
    QLineEdit  * lineEdit;
    QPushButton *  okButton ;
    QPushButton * cancelButton ;

public:
    GoToCellDialog(QWidget *parent = 0);

private slots:
    void on_lineEdit_textChanged();


};

#endif // GOTOCELLDIALOG_H

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cpp file
######################################################################
#include <QtGui>
#include "gotocelldialog.h"
#include <QtUiTools>

GoToCellDialog::GoToCellDialog(QWidget *parent)
    : QDialog(parent)
{
    //setupUi(this);
    QUiLoader loader;
    QFile file("gotocelldialog.ui");
    file.open(QFile::ReadOnly);
    QWidget *formWidget = loader.load(&file, this);
    file.close();

    /*
    QLineEdit *lineEdit=formWidget->findChild<QLineEdit *>("lineEdit");
    QPushButton *okButton = formWidget->findChild<QPushButton *>("okButton");
    QPushButton *cancelButton = formWidget->findChild<QPushButton *>("cancelButton");
    */

    this->LineEdit=formWidget->findChild<QLineEdit *>("lineEdit");
    this->okButton=formWidget->findChild<QPushButton *>("okButton");
    this->cancelButton=formWidget->findChild<QPushButton *>("cancelButton");

    QRegExp regExp("[A-Za-z][1-9][0-9]{0,2}");
    lineEdit->setValidator(new QRegExpValidator(regExp, this));
    connect(okButton, SIGNAL(clicked()), this, SLOT(accept()));
    connect(cancelButton, SIGNAL(clicked()), this, SLOT(reject()));
}
void GoToCellDialog::on_lineEdit_textChanged()
{
    this->okButton->setEnabled(this->lineEdit->hasAcceptableInput());
}


###########################
compilation:
###########################
/home/melmoth/dev/qt/testgit/home-melmoth-dev-qt-book-chapter2-dynamic/gotocelldialog.cpp:21: error: ‘class GoToCellDialog’ has no member named ‘LineEdit’