How to save a table in a file

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.

0_1531210402194_729a0dca-9bc9-4745-a532-9d41af2aef78-image.png

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);
       }

VRonin

Replace out<<ui->tableWidget->item(i, j)->text(); with out<<ui->tableWidget->model()->index(i, j).data().tostring(); to prevent segfaults

The problems I highlighted are still present though

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

In your code above you are not:

Writing any new line to separate rows.

Writing any column separator

Escaping column separators inside the data