Reading horizontal header item of QStandardItemModel

[vorlket]

With this set of codes rendering to a table view and enabling save to text file, I am having trouble reading the horizontal header labels. Reading the horizontal header item data returns nulls, and reading the header data leads to the program crashing.

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtSql>
#include <QStandardItemModel>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;
    QSqlDatabase db;
    QStandardItemModel *model;

private slots:
    void on_actionSave_As_triggered();
};

#endif // MAINWINDOW_H

mainwindow.cpp:

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

#include <QFileDialog>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    db = QSqlDatabase::addDatabase("QPSQL");
    db.setHostName("192.168.2.103");
    db.setPort(5433);
    db.setUserName("vorlket");
    db.setPassword("K1156312j");
    db.setDatabaseName("fxproj");

    if (db.open())
    {
        QSqlQuery query(db);
        if (query.exec("SELECT *, '' AS comment FROM audusd.ts_min_econevent ORDER BY min LIMIT 10000"))
        {
            model = new QStandardItemModel(query.size(), query.record().count(), this);
            QStringList header;
            int row = 0;
            while (query.next())
            {
                for (int column = 0; column < query.record().count(); ++column)
                {
                    if (row == 0)  header << query.record().fieldName(column);
                    QStandardItem *item = new QStandardItem(query.value(column).toString());
                    model->setItem(row, column, item);
                }
                ++row;
            }
            model->setHorizontalHeaderLabels(header);
        }
        ui->tableView->setModel(model);
    }
}

MainWindow::~MainWindow()
{
    db.close();
    delete ui;
}

void MainWindow::on_actionSave_As_triggered()
{
    QString fileName = QFileDialog::getSaveFileName(this, tr("Save Comment on Economic Event"), "", tr("CSV (*.csv);;All Files (*)"));

    QString textData;
    int rows = model->rowCount();
    int columns = model->columnCount();

    for (int j = 0; j < columns; j++)
    {
        // adding this line results in the program crashing: textData += model->headerData(columns, Qt::Horizontal).toString();
        textData += model->horizontalHeaderItem(columns)->data().toString();
        if (j < columns - 1) textData += "#";
    }
    textData += "\n";

    for (int i = 0; i < rows; i++)
    {
        for (int j = 0; j < columns; j++)
        {
            if (!model->data(model->index(i, j)).isNull())
            {
                textData += model->data(model->index(i, j)).toString();
                if (j < columns - 1) textData += "#";
            }
        }
        textData += "\n";
    }

    QFile csvFile(fileName);
    if (csvFile.open(QIODevice::WriteOnly | QIODevice::Truncate))
    {
        QTextStream out(&csvFile);
        out << textData;
        csvFile.close();
    }
}

[VRonin]

textData += model->horizontalHeaderItem(columns)->data().toString(); should become textData += model->horizontalHeaderItem(j)->data().toString();

[vorlket]

Yep, j instead of columns...

With columns replaced with j, model->headerData(j, Qt::Horizontal).toString(); works (don't know why model->horizontalHeaderItem(j)->data().toString(); doesn't work - it returns null).