Problem with saving function (overwrite file which saved by dialog)

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@Wieland

    QStandardPaths::writableLocation(QStandardPaths::GenericDataLocation);

    QFile file;
    file.setFileName(fileName);

    if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
       qDebug() << "Fehler beim Speichern der Datei";
    }

    QTextStream out(&file);
    out << toHtml();
    file.close();

This is my saveFunction without Dialog. This doesn't work. SaveUnder Function is same as i post earlier

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Okay, so this is your function:

void MainWindow::mySaveFunction() const
{
    QStandardPaths::writableLocation(QStandardPaths::GenericDataLocation);

    QFile file;
    file.setFileName(fileName);

    if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
        qDebug() << "Fehler beim Speichern der Datei";
    }

    QTextStream out(&file);
    out << toHtml();
    file.close();
}

I guessed it's a member function of something, let's assume this something is MainWindow. Next guess is toHtml is another member function. So, the following line does nothing:

QStandardPaths::writableLocation(QStandardPaths::GenericDataLocation);

And what about fileName? Is that a member variable?

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@Wieland
toHtml() is QString
fileName is QString

And yes, the function is of QMainWindow

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@Wieland
void MainWindow::mySaveFunction()

without const

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Maybe your fileName is wrong? Try this:

if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
{
  qDebug() << QString("Fehler beim Speichern der Datei: %1").arg(fileName);
}

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@Wieland

QFSFileEngine::open: No file name specified
"Fehler beim Speichern der Datei: "
QIODevice::write (QFile, ""): device not open

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@HenrikSt. Congrats, you just found your problem, fileName is empty :-)

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That good, i know..

But i don't know how to fix.
If you help me I am very happy :-)

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You must assign some useful value to fileName, e.g. like this:

void MainWindow::mySaveFunction()
{
    const QString path = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
    QFile file;
    fileName = QString("%1/%2").arg(path).arg("unbenannt.html");
    file.setFileName(fileName);

    if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
        qDebug() << QString("Fehler beim Speichern der Datei: %1").arg(fileName);
    }

    QTextStream out(&file);
    out << toHtml();
    file.close();
}

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@Wieland
Hi, this works, but the Problem is, that you create a new file ("unbenannt.html")

I want to overwrite the file i create with the Dialog before. You understand?

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@HenrikSt. In this case the name you assign to fileName here must exactly match the name of the existing file.

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@Wieland
I know... But every user enter another fileName so "unbenannt.htm" will not work..

Do you have another idea?

Thanks :)

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@HenrikSt. After the user entered the file name the first time, just save the name then and use it again later.

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@Wieland
Ah ok. I'm new in Qt. Can you write an example for this case that i can use it?

I have Problems with writing Code. Reading is no Problem. Do you have any tips for me?

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The following code isn't very elegant but I think it's good enough to serve as an example.

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    bool mySaveFunction();
    QString toHtml() const;

private slots:
    void saveFile();

private:
    Ui::MainWindow *ui;
    QString m_fileName;

};

#endif // MAINWINDOW_H

mainwindow.cpp

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

#include <QFile>
#include <QTextStream>
#include <QDebug>
#include <QStandardPaths>
#include <QFileDialog>
#include <QMessageBox>

bool MainWindow::mySaveFunction()
{
    // if this happens we have a bug in our code
    Q_ASSERT_X(!m_fileName.isEmpty(), "mySaveFunction", "m_fileName is empty");

    QFile file(m_fileName);
    if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
        QMessageBox::critical(this, "Fehler", QString("Fehler beim Speichern der Datei: %1").arg(m_fileName) );
        return false;
    }
    QTextStream out(&file);
    out << toHtml();
    file.close();
    QMessageBox::information(this, "Information", QString("Die Datei wurde gespeichert: %1").arg(m_fileName) );
    return true;
}


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(ui->pushButton, SIGNAL(clicked(bool)), this, SLOT(saveFile()));
}

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

QString MainWindow::toHtml() const
{
    return "<html></html>\n";
}

void MainWindow::saveFile()
{
    if (m_fileName.isEmpty()) {
        // first attempt to save the file
        m_fileName = QFileDialog::getSaveFileName(this, tr("Speichern unter..."),
                                        QString("Unbenannt.htm"), tr("TextPad 1.0 (*.htm);;"));
        if (m_fileName.isEmpty()) {
            return; // dialog was canceled
        }
    }
    if (!mySaveFunction()) {
        m_fileName.clear(); // saving failed. clear m_fileName so the QFileDialog will come up again next time
    }
}

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@Wieland
Hi, thank you for the example

if (!mySaveFunction()) {
        m_fileName.clear(); // saving failed. clear m_fileName so the QFileDialog will come up again next time
    }

This Code is not working...

C:\Users\Henrik\Documents\TextPad\pagestextedit.cpp:557: Fehler: could not convert 'PagesTextEdit::saveUnderDocument()' from 'void' to 'bool'
             if (!saveUnderDocument()) {
                                    ^

I have void MainWindow::save....
and not bool

How can i Change it?

One Problem is existing..
When i open a file e.g. from Desktop and i write something in and want to save it with mySaveFunction i get an runtime error...
Do you know why?

Thanks a lot

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@HenrikSt.
The Code which is not working i fixed it...

But the other Problem not

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@HenrikSt. said:

Do you know why?

No.

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@Wieland
https://onedrive.live.com/redir?resid=8CA2253BB1C9EA6!60243&authkey=!ABJFjbW9wpRomkw&v=3&ithint=photo%2Cpng

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@HenrikSt.
But you understand my Problem?