#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

class QPushButton;

class Widget : public QWidget
{
    Q_OBJECT
public:
    Widget(QWidget *parent = 0);

private:
    QPushButton *m_btn;

private slots:
    void changeBtnText(QString text);
};

#endif // WIDGET_H

#include "widget.h"

#include <QVBoxLayout>
#include <QLineEdit>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>

Widget::Widget(QWidget *parent)
    : QWidget(parent),
      m_btn(new QPushButton("btn"))
{
    QPushButton *btn2 = new QPushButton("btn #2");

    QLineEdit *lineEdit = new QLineEdit;
    connect(lineEdit, SIGNAL(textChanged(QString)), SLOT(changeBtnText(QString)));

    QHBoxLayout *btnLay = new QHBoxLayout;
    btnLay->addWidget(m_btn);
    btnLay->addWidget(btn2,1);

    QVBoxLayout *mainLay = new QVBoxLayout;
    mainLay->addLayout(btnLay);
    mainLay->addWidget(lineEdit);

    setLayout(mainLay);
}

void Widget::changeBtnText(QString text)
{
    m_btn->setText(text);
}