Populating a table in Qt

Question

I'm trying to improve this example for a diagram editor.

The example uses a nodes class with a few attributes unrelated to my needs. Right now I want to add a "list of arrays" to this node class in order to then populate a QTableView in the "properties" dialog. I already designed the properties dialog with the QTableView. I'm not even sure this is feasible/makes sense.

Basically the table must have 4 columns: name, type, value and unit.

Each row of the table is a certain "property" I need the node to have.

My question is: how can/should I model the table at class level? I ask this because I have been looking to QList, QVariant, QMap, QMultiMap and I can't figure out out to use them correctly, and none of the examples I found so far are any help either, at least for what I need to do. I saw something about the QStandardItemModel class, and I think it relates to the solution, but I can't understand how/why.

To top it off, I'm a Qt/C++ beginner, so much of the dynamics and jargon in Qt/C++ are still elluding me.

If anyone could give me some pointers, that would be great.

EDIT: This isn't getting much attention, and I don't know if its because I wasn't clear enough, but anyway, try to picture this:

• a Node has a PropertyList
• that PropertyList lists Properties
• Properties are sort of dictionaries, as they have always 4 attributes and respective values: name:(string), type:(string), value:(double) and unit:(string).
• one Node can only have one PropertyList; a PropertyList can have several Properties. Some Nodes will have 3 properties, others will have 4, etc...

Now, the Nodes are represented in a diagram via a QGraphicsScene with QGraphicsItem. You can access a PropertiesDialog widget that has a QTableWidget in it. This table will show the PropertyList.

I want to know what kind of "structure" I can create/define that enables me to easily insert/read data in the table widget - ie, I load the data into the PropertiesList of the Node and it shows up in the table widget; if I change the data in the table widget, it passes on to the PropertiesList of the Node.

Hope this helps clearing out any doubts that may arise.

Answer 1

Well, after a lot of hair pulling, I got what I needed.

My first step was to create a Property class. This class has functions to set or get a name string, a type string, a value double and a unit string.

Next, I updated the Node class to include functions to add and remove Property object pointers to a QList<Property *>. Also included was a listProperties function that returns all the Property objects from a certain Node.

After this, the function to populate the QTableWidget with a certain Node's properties was coded like this:

    propertiesList = node->listMyProperties();

    for (int row = 0; row < propertiesList.size(); ++row) {
        Property *property = propertiesList.at(row);
        addRow();
        tableWidget->item(row, 0)->setData(Qt::DisplayRole, property->propertyName());
        tableWidget->item(row, 1)->setData(Qt::DisplayRole, property->propertyType());
        tableWidget->item(row, 2)->setData(Qt::DisplayRole, property->propertyValue());
        tableWidget->item(row, 3)->setData(Qt::DisplayRole, property->propertyUnit());
    }

And the addRow() function:

void PropertiesDialog::addRow()
{
    int row = tableWidget->rowCount();

    tableWidget->insertRow(row);

    QTableWidgetItem *item0 = new QTableWidgetItem;
    item0->setTextAlignment(Qt::AlignRight | Qt::AlignVCenter);
    tableWidget->setItem(row, 0, item0);

    QTableWidgetItem *item1 = new QTableWidgetItem;
    item1->setTextAlignment(Qt::AlignRight | Qt::AlignVCenter);
    tableWidget->setItem(row, 1, item1);

    QTableWidgetItem *item2 = new QTableWidgetItem;
    item2->setTextAlignment(Qt::AlignRight | Qt::AlignVCenter);
    tableWidget->setItem(row, 2, item2);

    QTableWidgetItem *item3 = new QTableWidgetItem;
    item3->setTextAlignment(Qt::AlignRight | Qt::AlignVCenter);
    tableWidget->setItem(row, 3, item3);

    tableWidget->setCurrentItem(item0);
}

This produces what I needed: to have a class to hold the property values related to each node, and present them on a QTableWidget. Next step is to make the reverse path, meaning, when edits occur in the QTableWidget, those changes should propagate to the class. Now I think I can find my way, hope this helps anyone trying to find something related. I'll also update the tags and maybe edit the title to make it more relevant/meaningful.