Save QTreeView/QStandardItemModel with DataStream to file?

[JonB]

@StudentScripter
Not sure quite what you are expecting. You can never serialize either of QTreeView or QStandardItemModel to stream as they derive from QObject. So it's up to you to write code to save whatever you want from these in some format to file and reconstruct on load.

[StudentScripter]

@JonB Well than let me ask another question in this case, cause i don't know how:

How could save all items with childrens (obviously some kind of loop) and reconstruct that?

[mpergand]

@StudentScripter said in Save QTreeView/QStandardItemModel with DataStream to file?:

How could save all items with childrens (obviously some kind of loop)

It's called recursion.
You need to build a binary tree data structure for that,
see Simple tree model example

[StudentScripter]

@mpergand Thank you very much. Another problem:

I already write data to a file using QDatastream, in the same file i want to save the data for my qtreeview. How can i do it that the loading and saving works properly and does not override or read wrong data from the file?

[mpergand]

@StudentScripter said in Save QTreeView/QStandardItemModel with DataStream to file?:

I already write data to a file using QDatastream, in the same file i want to save the data for my qtreeview

I'm not sure to understand what you mean, sorry.

[StudentScripter]

@mpergand I have already setup a datastream where i write data from a QGraphicsScene to a file, now i wanted to save the data of the QTreeView in the same file without overriding the data of the QGraphicsScene.
Also in the reading process I have to make sure somehow that i only read the right data from the file, that is intended for my QTreeView.

Hope this helps, and thanks for trying to help me out.

[SGaist]

@StudentScripter hi,

It is your responsibility to properly setup the sequence when you write and read.

Basically, you write each widget/model/whatever always in the same order and you do the same when you load from the file.

[StudentScripter]

@SGaist But how can i set a sequence? How can let it write all the data of the scene first to the file and than the data of the treeview.

How do i than determine till where to read the scene data and where and when to begin reading the QtreeView data?

[Christian Ehrlicher]

@StudentScripter said in Save QTreeView/QStandardItemModel with DataStream to file?:

How do i than determine till where to read the scene data and where and when to begin reading the QtreeView data?

That's exactly your task you have to find out. It's called 'programming'

[JonB]

@StudentScripter
Like we said, it's your duty to write that code. So you know where e.g. the scene data ends so that the treeview data can begin.

QDataStream just lets you write (binary) data to a file, i.e. it's concerned with how to write an integer or a string. I would suggest you consider saving your data as either XML or JSON. (They happen to save as text, but that's not really the issue here.) That will allow you more easily to place structure on what you save, so that e.g. you can recognise where the scene data ends and the treeview data begins.

[StudentScripter]

@JonB @SGaist

Well, i understand that my request before sounded wacky, sorry for that. I tried inserting a string as marker to differentiate where which data begins but somehow it wasn't able to read that correctly, it didn't worked. Please give me a hint on how to differentiate between different data in qdatastream files, i want to stick to that format if possible.

I have a main save methode from where i trigger the save scene first and the save qtreeview second:

//Save Action in der Menuleiste, ermöglicht save in der GraphicsScene
void MainWindow::saveActionTriggered()
{
    QString filename = QFileDialog::getSaveFileName(this, tr("Save File"), 
                                            "", 
                                            tr("MyEditor (*.xle)"));
                                            
    if(!filename.isNull())
    {
        scene->saveScene(filename);
                            //Saven der ViewLayerList
                            ViewLayerList *LayerList = this->findChild<ViewLayerList *>("UNQViewLayerList");
                            LayerList->saveTreeView(filename);
    }                                       
}


//Load Action in der menuleiste, ermöglicht load in der GraphicsScene
void MainWindow::loadActionTriggered()
{
    QMessageBox::StandardButton reply;
        reply = QMessageBox::warning(this, "Caution", "Loading a file will clear your current project, \ndo you want to save it first?",
                                    QMessageBox::Yes|QMessageBox::No);                                 
        if (reply == QMessageBox::No) 
        {    
            QString filename = QFileDialog::getOpenFileName(this, tr("Open File"), 
                                                        "", 
                                                        tr("MyEditor (*.xle)")); 
            if(!filename.isNull())
            {   
                scene->loadScene(filename);
                
                            //Laden der ViewLayerList
                            ViewLayerList *LayerList = this->findChild<ViewLayerList *>("UNQViewLayerList");
                            LayerList->loadTreeView(filename);
            }
        }
}

And here ist the load/save methode from my qtreeview:

    
void ViewLayerList::saveTreeView(QString &filename)
{
    qDebug() << "SaveAction TreeView";
    QFile file(filename);
    
    if(!file.open(QIODevice::WriteOnly | QIODevice::Append))
        return;
    
    QDataStream dataStream(&file);
    int rowCount = model->rowCount();
    int columnCount = model->columnCount();
    dataStream << rowCount;
    dataStream << columnCount;
 
    for(int row = 0; row < rowCount; row++)
        for(int column = 0; column < columnCount; column++) {
        dataStream << model->item(row, column)->text();
 
 
        }
    
    file.close();
}





void ViewLayerList::loadTreeView(QString &filename)
{
    qDebug() << "LoadAction TreeView";
    
    //File laden und öffnen
    QFile file(filename);
    if(!file.open(QIODevice::ReadOnly))
        return;

    QDataStream dataStream(&file);
    
    int rowCount, columnCount;
    dataStream >> rowCount;
    dataStream >> columnCount;
 
    for(int row = 0; row < rowCount; row++)
        for(int column = 0; column < columnCount; column++) {
        QString item;
        dataStream >> item;
        QStandardItem * w_item = new QStandardItem(item);
        model->setItem(row, column, w_item);
 
      }
   

      
   

    file.close();
}

The code does work on it's own but breaks when second data is saved from my graphicsscene, i guess cause it cannot differentiate.

[mpergand]

@StudentScripter
You save your tree as a flat array, then you loose any parent/child relationship.

[StudentScripter]

@mpergand I know i've just done that for now to simpliefy the process as my main problem for now is getting both different data saved and loaded from within the same file.

[JonB]

@StudentScripter

@JonB said in Save QTreeView/QStandardItemModel with DataStream to file?:

I would suggest you consider saving your data as either XML or JSON.

That would encapsulate the tree structure. personally I don't like the idea of a binary data stream with some "markers" you have tried to put in it as "separators". You seem to be only saving string data from your model anyway. Perhaps a touch more initial work, easier to work with in the long run. Don't forget that if you get one thing wrong in binary data it's basically non-recoverable, XML/JSON is easily addressed in a text correction if required.

[StudentScripter]

@JonB Well but if i have doesn't xml files i can't load/save a projectfile. I want a binary file with all data in it so it functions as a project file. Also i need to save: EditRole, CheckStateRole, DecorationRole, a few UserRoles.

[mpergand]

@StudentScripter
The principle to save/load a binary tree is always the same.
Starting with the root item, for each item you need to:

• save its data
• save the nb of children
• save the children items ( looks like we have some recursion here)

For loading, you have to reverse the process:

• create a item
• set its data
• get the nb of children
• create the children ( recursion again)

[StudentScripter]

@mpergand Yes i really appreciate your answer, but that wasn't actually the point of my question yet. I just wanted to know: how do differentiate data within a binary?

How can i determine till where to read the data for my graphicsscene and where to start reading the data for my qtreeview?

Or to formulate it different:
Lets say I add an String named "MARKER" into my datastream and write this string to file. I want the datastream to search for this string and only read data after this string.

[mpergand]

@StudentScripter
Your are talking about two different objects, a graphic scene and a treeview and you seems to save their data to the same file, maybe saving them to two separate files may be a solution ?

[StudentScripter]

@mpergand No it has to be the same file, because i want to able to load from one projectfile. I found that using a qint32 as marker works. First i wanted to use a string but somehow qdatastreams to be unable to find a qstring.

Here is what i've done: (This works)

   
void ViewLayerList::saveTreeView(QString &filename)
{  

    qDebug() << "SaveAction TreeView";
    QFile file(filename);
    
    if(!file.open(QIODevice::WriteOnly | QIODevice::Append))
        return;
    
    QDataStream dataStream(&file);


    dataStream <<  qint32(0xDEADBEEF);  // Write a separator or marker to indicate the end of the first data set

    
    
    
    int rowCount = model->rowCount();


    dataStream << rowCount;

 
    for(int row = 0; row < rowCount; row++)
    {
        //dataStream << model->item(row, 1)->text();
    
 
    }
    

    file.close();
}





void ViewLayerList::loadTreeView(QString &filename)
{
    qDebug() << "LoadAction TreeView";
    
    // File laden und öffnen
    QFile file(filename);
    if (!file.open(QIODevice::ReadOnly))
        return;

    QDataStream dataStream(&file);


    
    
    while (!dataStream.atEnd()) {
        qint32 test;
        dataStream >> test;

          
        if (test == qint32(0xDEADBEEF)) {
            qDebug() << "Marker Found";
            break;  // Exit the loop after finding the marker
        }
    }

    if (dataStream.atEnd()) {
        qDebug() << "Error: Marker not found or end of file reached";
        file.close();
        return;
    }


        // 11. Data in dem File
        int rowCount;
        dataStream >> rowCount;

        for(int row = 0; row < rowCount; row++) {
            QStandardItem *w_item = new QStandardItem();
            model->setItem(row, 0, w_item);
        }
    

    file.close();
}

[mpergand]

@StudentScripter
You can use a QBuffer instead.
Save your data to two separate buffers, then save them to a file with at the start of the file, the offset of the second buffer where it is located in the file.