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

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  • ? A Former User

    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?

    ? Offline
    ? Offline
    A Former User
    wrote on last edited by
    #7

    @Wieland
    toHtml() is QString
    fileName is QString

    And yes, the function is of QMainWindow

    1 Reply Last reply
    0
    • ? A Former User

      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?

      ? Offline
      ? Offline
      A Former User
      wrote on last edited by
      #8

      @Wieland
      void MainWindow::mySaveFunction()

      without const

      1 Reply Last reply
      0
      • ? Offline
        ? Offline
        A Former User
        wrote on last edited by
        #9

        Maybe your fileName is wrong? Try this:

        if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
        {
          qDebug() << QString("Fehler beim Speichern der Datei: %1").arg(fileName);
        }
        
        ? 1 Reply Last reply
        0
        • ? A Former User

          Maybe your fileName is wrong? Try this:

          if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
          {
            qDebug() << QString("Fehler beim Speichern der Datei: %1").arg(fileName);
          }
          
          ? Offline
          ? Offline
          A Former User
          wrote on last edited by
          #10

          @Wieland

          QFSFileEngine::open: No file name specified
          "Fehler beim Speichern der Datei: "
          QIODevice::write (QFile, ""): device not open
          
          ? 1 Reply Last reply
          0
          • ? A Former User

            @Wieland

            QFSFileEngine::open: No file name specified
            "Fehler beim Speichern der Datei: "
            QIODevice::write (QFile, ""): device not open
            
            ? Offline
            ? Offline
            A Former User
            wrote on last edited by
            #11

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

            1 Reply Last reply
            0
            • ? Offline
              ? Offline
              A Former User
              wrote on last edited by
              #12

              That good, i know..

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

              ? 1 Reply Last reply
              0
              • ? A Former User

                That good, i know..

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

                ? Offline
                ? Offline
                A Former User
                wrote on last edited by
                #13

                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();
                }
                
                ? 1 Reply Last reply
                1
                • ? A Former User

                  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();
                  }
                  
                  ? Offline
                  ? Offline
                  A Former User
                  wrote on last edited by
                  #14

                  @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?

                  ? 1 Reply Last reply
                  0
                  • ? A Former User

                    @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?

                    ? Offline
                    ? Offline
                    A Former User
                    wrote on last edited by
                    #15

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

                    ? 1 Reply Last reply
                    0
                    • ? A Former User

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

                      ? Offline
                      ? Offline
                      A Former User
                      wrote on last edited by
                      #16

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

                      Do you have another idea?

                      Thanks :)

                      ? 1 Reply Last reply
                      0
                      • ? A Former User

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

                        Do you have another idea?

                        Thanks :)

                        ? Offline
                        ? Offline
                        A Former User
                        wrote on last edited by
                        #17

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

                        ? 1 Reply Last reply
                        0
                        • ? A Former User

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

                          ? Offline
                          ? Offline
                          A Former User
                          wrote on last edited by
                          #18

                          @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?

                          ? 1 Reply Last reply
                          0
                          • ? A Former User

                            @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?

                            ? Offline
                            ? Offline
                            A Former User
                            wrote on last edited by
                            #19

                            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
                                }
                            }
                            
                            ? 1 Reply Last reply
                            1
                            • ? A Former User

                              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
                                  }
                              }
                              
                              ? Offline
                              ? Offline
                              A Former User
                              wrote on last edited by
                              #20

                              @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

                              ? ? 2 Replies Last reply
                              0
                              • ? A Former User

                                @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

                                ? Offline
                                ? Offline
                                A Former User
                                wrote on last edited by
                                #21

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

                                But the other Problem not

                                1 Reply Last reply
                                0
                                • ? A Former User

                                  @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

                                  ? Offline
                                  ? Offline
                                  A Former User
                                  wrote on last edited by
                                  #22

                                  @HenrikSt. said:

                                  Do you know why?

                                  No.

                                  ? 1 Reply Last reply
                                  0
                                  • ? A Former User

                                    @HenrikSt. said:

                                    Do you know why?

                                    No.

                                    ? Offline
                                    ? Offline
                                    A Former User
                                    wrote on last edited by
                                    #23

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

                                    ? 1 Reply Last reply
                                    0
                                    • ? A Former User

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

                                      ? Offline
                                      ? Offline
                                      A Former User
                                      wrote on last edited by
                                      #24

                                      @HenrikSt.
                                      But you understand my Problem?

                                      1 Reply Last reply
                                      0
                                      • jsulmJ Online
                                        jsulmJ Online
                                        jsulm
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #25

                                        The cause for that crash can be everything!
                                        How should anybody know what it is without your code?
                                        Did you try to debug your program to see where it crashes?

                                        https://forum.qt.io/topic/113070/qt-code-of-conduct

                                        1 Reply Last reply
                                        0

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