class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    QWidget *pMainWidget;
    QHBoxLayout *pMainLayout;
    QSettings *pSetting;

    QLabel *pLabel;
    QPushButton *pButtonShow;
    QPushButton *pButtonSet;
    QLineEdit *pLineEdit;

    QString pSettingFile;

public slots:
    void showSettingData();
    void setData();
};

#include "mainwindow.h"
#include <QtCore/QCoreApplication>
#include <QApplication>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{

    pMainWidget = new QWidget (parent);
    pMainLayout = new QHBoxLayout(pMainWidget);

    pLabel      = new QLabel("Output comes here",pMainWidget);
    pLineEdit   = new QLineEdit();
    pButtonShow = new QPushButton("Show", pMainWidget);
    pButtonSet  = new QPushButton("Set", pMainWidget);

    setCentralWidget(pMainWidget);
    pMainWidget->setLayout(pMainLayout);
    pMainLayout->addWidget(pLabel);
    pMainLayout->addWidget(pButtonShow);
    pMainLayout->addWidget(pLineEdit);
    pMainLayout->addWidget(pButtonSet);

    pSettingFile = QApplication::applicationDirPath()+"settings.ini";

    QObject::connect(pButtonShow, SIGNAL(clicked()), this, SLOT(showSettingData()));
    QObject::connect(pButtonSet, SIGNAL(clicked()), this, SLOT(setData()));

}

MainWindow::~MainWindow()
{

}

void MainWindow::setData()
{
    QSettings Setting(pSettingFile, QSettings::NativeFormat);

    QString data = pLineEdit->text();
    Setting.setValue("baseurl", data);
}

void MainWindow::showSettingData()
{
    QSettings Setting(pSettingFile, QSettings::NativeFormat);

    if (Setting.contains("baseurl"))
    {
        QString data = Setting.value("baseurl").toString();
        pLabel->setText(data);
    }

}

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

Setting.setValue("baseurl", data);
Setting.sync();