How to save a table in a file

[Daesos]

Hello. I'm new here, but i've already read many topic of this forum.
I'm creating a program that monitors a directory.
I've searched for a method to save a tablewidget to a file and this is what I've made:

void MainWindow::on_pushButton_2_clicked()
{
QFile csv("log_activity.csv");

if(!csv.open(QFile::WriteOnly))
    return;

QTextStream out(&csv);

for(int i = 0; i < ui->tableWidget->rowCount(); ++i)
    for (int j = 1; j < ui->tableWidget->columnCount(); j++)
        out<<ui->tableWidget->item(i, j)->text();

csv.close();
}

This is my tablewidget:

The problem is that once i click on the save button (pushButton_2) the program doesn't save anything in the file. What am i missing?

[VRonin]

I'm developing a library that includes this feature: https://github.com/VSRonin/QtModelUtilities
I still need to get it to stable and fully documented but should be good enough for rock and roll.
Saving to csv is done via the CsvModelSerialiser class

[Daesos]

I'd like to not implement other libraries. I want to resolve this only with given libraries by Qt.

[jsulm]

@Daesos Are you sure it does not save the file? You're using a relative path, that means the file will be located in the current working directory of your app, most probably in the build directory. Also did you check whether MainWindow::on_pushButton_2_clicked() was actually called?

[Daesos]

The image above is the directory of my project. If I click on save button, the cell corresponding to log_activity.csv and Event changes into modified.
It shows "Modified" when the date of the previous directory is different from the current one.
So I guess the save_button works.

Also, if the file doesn't exit, the program create the file with the given name.

[VRonin]

@Daesos said in How to save a table in a file:

I want to resolve this only with given libraries by Qt

Then copy-paste my code. I only use Qt in those and license is apache 2 so you can basically do what you want with it.

In your code above you are not:

• Writing any new line to separate rows.
• Writing any column separator
• Escaping column separators inside the data

[jsulm]

@Daesos Did you try to debug? Especially the nested for loops?

[JonB]

@Daesos
Assuming the file is opened for write, you are saying you end up with nothing in it, and your table does indeed contain desired text (ui->tableWidget->item(i, j)->text()). You stream all your data to QTextStream out but you only close the QFile csv. I don't know if that knows to fetch all remaining data out of the stream. Try out.flush() prior to the csv.close()?

[Daesos]

@jsulm I'm trying, but it stops with this message: Stopped "end-stepping-range". I've put a breakpoint at "out<<ui->tableWidget->item(i, j)->text();" and as i can see, this returns "main.window.cpp", which is correct. Then, I don't what happen.

[jsulm]

@Daesos Try calling http://doc.qt.io/qt-5/qtextstream.html#flush before closing the file

[Daesos]

@jsulm Already did, and nothing changed.

[jsulm]

@Daesos Last idea I have: is it possible that you open same file somewhere else in your app, or that there is still an instance of your app running?
Oh, one more idea: try to write the file using an absolute path to some other location.

[Daesos]

@jsulm I checked and there is no other instance opened. Also, I used another path. The program created the file.csv (empty), then quitted. Application Output: "The program has unexpectedly finished."

Since I don't know if I have mistaken something I will post all the mainwindow.cpp code:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QFileInfo>
#include <QTimer>
#include <QDateTime>
#include <QFile>
#include <QTextStream>

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

    setWindowTitle("DirectoryMonitor");
    ui->tableWidget->setColumnCount(4);
    ui->tableWidget->setHorizontalHeaderLabels(QStringList() << "" << "Filename" << "Event" << "Time");

    f_name = "log_activity.csv";
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
    ui->tableWidget->clearContents();
    path = QFileDialog::getExistingDirectory(this, tr("Open Directory"), ".", QFileDialog::ShowDirsOnly | QFileDialog::DontResolveSymlinks);
    ui->lineEdit->setText(path);

QDir dir(path);

dir.setFilter(QDir::Dirs | QDir::Files | QDir::NoDotAndDotDot);
dir.setSorting(QDir::Time);
list = dir.entryInfoList();

for(int i = 0; i < list.size(); ++i){
        ui->tableWidget->insertRow(ui->tableWidget->rowCount());
        ui->tableWidget->setItem(i, 1, new QTableWidgetItem(list.at(i).fileName()));
        ui->tableWidget->setItem(i, 3, new QTableWidgetItem(list.at(i).lastModified().toString()));
}

int count = 0;

for(int i = 0; i < ui->tableWidget->rowCount(); ++i){
    QTableWidgetItem *itm = ui->tableWidget->item(i, 1);
    if(itm != 0)
       ++count;
}
//rimuovi righe vuote
ui->tableWidget->setRowCount(count);

QTimer *time = new QTimer(this);

connect(time, SIGNAL(timeout()), this, SLOT(changes()));
time->start(3000);
}

void MainWindow::changes()
{
QDir dir(path);
dir.setFilter(QDir::Dirs | QDir::Files | QDir::NoDotAndDotDot);
dir.setSorting(QDir::Time);

QFileInfoList newlist = dir.entryInfoList();

int index_delete = -1;

//caso modified e delete file
for(int i = 0; i < list.size(); ++i){
    int count = 0;
    for(int j = 0; j < newlist.size(); ++j){
        if(list.at(i).fileName() == newlist.at(j).fileName()){
            ++count;
            if(list.at(i).lastModified() != newlist.at(j).lastModified()){
                QTableWidgetItem *itm = new QTableWidgetItem("");
                itm->setBackground(QColor(109, 158, 235));
                ui->tableWidget->setItem(i, 0, itm);
                ui->tableWidget->setItem(i, 2, new QTableWidgetItem("Modified"));
                ui->tableWidget->setItem(i, 3, new QTableWidgetItem(newlist.at(j).lastModified().toString()));
            }
        }
    }
    if(count == 0){
        index_delete = i;
    }
}

if(index_delete != -1){
    QTableWidgetItem *itm = new QTableWidgetItem("");
    itm->setBackground(QColor(224, 102, 99));
    ui->tableWidget->setItem(index_delete, 0, itm);
    if(ui->tableWidget->item(index_delete, 2)->text() != "Deleted")
        ui->tableWidget->setItem(index_delete, 3, new QTableWidgetItem(QDateTime::currentDateTime().toString()));
    ui->tableWidget->setItem(index_delete, 2, new QTableWidgetItem("Deleted"));
}

//caso new file
int index_new = -1;

for(int i = 0; i < newlist.size(); ++i){
    int count = 0;
    for(int j = 0; (j < list.size() && count == 0); ++j){
        if(newlist.at(i).fileName() == list.at(j).fileName())
            ++count;
    }
    if(count == 0)
        index_new = i;
}

if(index_new != -1){
    ui->tableWidget->insertRow(ui->tableWidget->rowCount());
    QTableWidgetItem *itm = new QTableWidgetItem("");
    itm->setBackground(QColor(148, 195, 123));
    ui->tableWidget->setItem(ui->tableWidget->rowCount() - 1, 0, itm);
    ui->tableWidget->setItem(ui->tableWidget->rowCount() - 1, 1, new QTableWidgetItem(newlist.at(index_new).fileName()));
    ui->tableWidget->setItem(ui->tableWidget->rowCount() - 1, 2, new QTableWidgetItem("Created"));
    ui->tableWidget->setItem(ui->tableWidget->rowCount() - 1, 3, new QTableWidgetItem(newlist.at(index_new).lastModified().toString()));
    list.append(newlist.at(index_new));
}
}
void MainWindow::on_pushButton_2_clicked()
{
QFile csv(f_name);

if(!csv.open(QFile::WriteOnly))
    return;

QTextStream out(&csv);

for(int i = 0; i < ui->tableWidget->rowCount(); ++i)
    for (int j = 1; j < ui->tableWidget->columnCount(); j++){
        QString txt(ui->tableWidget->item(i, j)->text());
        out<<txt;
    }
out.flush();
csv.close();
}

Sorry for the indentation.
This is the declaration of the global variables in mainwindow.h

QString path, f_name;
QFileInfoList list;

[jsulm]

@Daesos Start your app with debugger (F5) and when it crashes check the stack trace to see where it crashes (use debug build of your app).

[J.Hilk]

@Daesos
Going through your code, I noticed, you're mixing postfix, prefix in your nested loop to access the Tablewidget Item. I would search there for an out of bounds error.

[JonB]

@Daesos
If you're still having problems with the file (once you've solved the "crash"), try replacing your QFile with a QString, and use https://doc.qt.io/Qt-5/qtextstream.html#QTextStream-3. You should be successfully building up the string of the file content. If that doesn't work, nor will write to file.

[Daesos]

I used debugger and when i click on pushButton_2 (save on interface) it returns a Segmentation Fault at "QTableWidgetItem::text".
@J.Hilk, I didn't even notice. I edited the increment.

Segmentation Fault occurs when I try to access to a NULL pointer, right? So, it might be out of bound.

[JonB]

@Daesos
I don't see save_button in the code you've posted?

I notice you have:

                ui->tableWidget->setItem(i, 0, itm);
                ui->tableWidget->setItem(i, 2, new QTableWidgetItem("Modified"));
                ui->tableWidget->setItem(i, 3, new QTableWidgetItem(newlist.at(j).lastModified().toString()));

Where do you setItem() on i, 1 ?

for(int i = 0; i < ui->tableWidget->rowCount(); ++i)
    for (int j = 1; j < ui->tableWidget->columnCount(); j++){
        QString txt(ui->tableWidget->item(i, j)->text());
        out<<txt;
    }

Check your accesses on every i, j here. Somewhere you do not have an item at item(i, j)!

[Daesos]

I've edited the increment:

   for(int i = 0; i < ui->tableWidget->rowCount(); ++i)
       for (int j = 1; j < ui->tableWidget->columnCount(); ++j)
           out<<ui->tableWidget->item(i, j)->text();

@JonB said in How to save a table in a file:

@Daesos

I notice you have:

                ui->tableWidget->setItem(i, 0, itm);
                ui->tableWidget->setItem(i, 2, new QTableWidgetItem("Modified"));
                ui->tableWidget->setItem(i, 3, new QTableWidgetItem(newlist.at(j).lastModified().toString()));

Where do you setItem() on i, 1 ?

I've inizialized item at (i, 1) before. Once inizialized the name of the file must not be modified. So I didn't use setItem on i, 1 again.

@Daesos
ui->tableWidget->setItem(ui->tableWidget->rowCount() - 1, 1, new QTableWidgetItem(newlist.at(index_new).fileName()));

[J.Hilk]

@Daesos said in How to save a table in a file:

for(int i = 0; i < ui->tableWidget->rowCount(); ++i)
for (int j = 1; j < ui->tableWidget->columnCount(); ++j)
out<<ui->tableWidget->item(i, j)->text();

Maybe it's time to #include good old <QDebug>

for(int i = 0; i < ui->tableWidget->rowCount(); ++i)
       for (int j = 1; j < ui->tableWidget->columnCount(); ++j){
           qDebug() << i << "of" << ui->tableWidget->rowCount() << endl
                             << j << "of" << ui->tableWidget->columnCount();
           out<<ui->tableWidget->item(i, j)->text();
           qDebug() << QString("Found text at %1 | %2").arg(i).arg(j);
       }