custom model isn't completely working

[mzimmers]

@JonB my setData() is patterned after the example I mentioned in my first post. I see what you're saying (I think), and I should probably fix that, but it doesn't seem to be influencing the code execution (according to the telltales).

Nowhere in my qml am I calling setData(); remember, I don't want my app to change anything (like the power state); merely to send a request to the back end for that change, and properly handle the response.

Thanks...

[JoeCFD]

@mzimmers did you try to add
beginResetModel();
set list data.....
endResetModel();

[mzimmers]

@JoeCFD hmm...I think you're on to something.

I created a setList() function (also patterned after the example) that contains those calls:

void EquipmentModel::setList(EquipmentList *list)
{
    beginResetModel();
    if (m_list != nullptr) {
        m_list->disconnect(this);
    }

    m_list = list;

    if (m_list != nullptr) {
        connect(m_list, &EquipmentList::preItemAppended, this, [=]() {
            const int index = m_list->equipment().size();
            beginInsertRows(QModelIndex(), index, index);
        });
        connect(m_list, &EquipmentList::postItemAppended, this, [=]() {
            endInsertRows();
        });

        connect(m_list, &EquipmentList::preItemRemoved, this, [=](int index) {
            beginRemoveRows(QModelIndex(), index, index);
        });
        connect(m_list, &EquipmentList::postItemRemoved, this, [=]() {
            endRemoveRows();
        });
    }
    endResetModel();
}

But...I never call it. I can try to modify my setData() to use it, though it will be tricky, as my list is a QObject, so I can't copy it. What do you think?

EDIT:

I modified this portion of my setData() as follows; still not getting the changes in the displays:

beginResetModel();
if (m_list->setItemAt(index.row(), item)) {
    qDebug() <<  __PRETTY_FUNCTION__ << "setItemAt() returned successfully; role is" << role;
    emit dataChanged(index, index, QVector<int>() << role);
    rc = true;
} else {
    qWarning() << __PRETTY_FUNCTION__ << "error from setItemAt.";
}
endResetModel();

I could move the begin/endResetModel() calls to the setItemAt() function, but I think the results would be the same, right?

[JoeCFD]

@mzimmers
https://doc.qt.io/qt-6/qabstractitemmodel.html#beginResetModel
When a model is reset it means that any previous data reported from the model is now invalid and has to be queried for again. This also means that the current item and any selected items will become invalid.

When a model radically changes its data it can sometimes be easier to just call this function rather than emit dataChanged() to inform other components when the underlying data source, or its structure, has changed.

You must call this function before resetting any internal data structures in your model or proxy model.

[mzimmers]

@JoeCFD it's as though the QML property that reflects the state just isn't getting the message to update. I wonder if there's something wrong with how I'm setting that property:

Rectangle {
    id: fakeSwitch
    height: 30; width: 30
    property bool switchState: equipmentModel.getEquipmentItem(pumpUuid).powerState // does this look OK?
    color: switchState ? 'green' : 'gray'
    MouseArea {
        anchors.fill: parent
        onClicked: {
            fakeSwitch.switchState = !fakeSwitch.switchState
            equipmentModel.sendSwitchChange(pumpUuid, fakeSwitch.switchState)
        }
    }
}

[JonB]

@mzimmers said in custom model isn't completely working:

property bool switchState: equipmentModel.getEquipmentItem(pumpUuid).powerState // does this look OK?

One thing. Your C++ code shows this is not a bool property, you test/set powerState() against Equipment::POWER_OFF/POWER_ON. Do these values convert correctly to bool?

[mzimmers]

Another data point in this little mystery: I have 3 locations in my GUI that show the value of this model element. Two are in ordinary screens, and they're not updating correctly. The third is in a drawer, and it's always correct. The Switch code is virtually identical. Does the act of opening a drawer force an update to its contents? Is that why that one is always right?

[mzimmers]

@JonB I think it is. I started using that FakeSwitch because I couldn't tell whether the real Switch was self-updating, and giving me a red herring. Here's the code from the real Switch, and its behavior is essentially the same (nothing in the custom switch affects this issue):

Switch_custom {
    id: cardSwitch
    visible: card.switchable
    checked: equipmentModel.getEquipmentItem(uuid).powerState === 1
    Layout.alignment: Qt.AlignRight
    onClicked: {
        console.log("EquipmentCard.qml: switch clicked; value is " + cardSwitch.checked)
        equipmentModel.sendSwitchChange(card.uuid, cardSwitch.checked)
    }
}

[JoeCFD]

@mzimmers What is the role type of drawer? I guess there is a default role.

[mzimmers]

@JoeCFD I don't assign any role to anything in the drawer. I'm not sure how I'd even do that as it relates to the Switch it contains.

[J.Hilk]

@mzimmers said in custom model isn't completely working:

Does the act of opening a drawer force an update to its contents?

possibly that opening the drawer recreates the drawer content, forcing a reload of the data each time its opened

[mzimmers]

@J-Hilk well, in a sense, that's good news -- it would mean that my model isn't properly signaling changes at all, so at least the problem is consistent.

This is so weird -- it's almost as though the Switches on the different screens are independent of each other. Everything in the model seems to be working, from messaging the server, to accepting the response and (seemingly) sending the appropriate signals to QML.

I know this idea is a cheat, and I wouldn't want to use it in production, but...is there a way to force a QML component to update every time it becomes visible?

[JoeCFD]

@mzimmers

 onVisibleChanged: {
      console.log( " visible =", visible )
      //do update if visible is true 
 }

[mzimmers]

@JoeCFD the Creator doesn't like the "do update" construct; am I supposed to replace update with something?

[JoeCFD]

@mzimmers these are only texts. You do your update there.

[mzimmers]

@JoeCFD OK, but what is the command to force the update?

Here's what's happening: in my model, I make the change at the appropriate time:

if (m_list->setItemAt(i, itemFromList)) {
    QModelIndex qmi = index(i, 0, QModelIndex());
    setData(qmi, itemFromList.powerState(), StateRole);
    qDebug() << __PRETTY_FUNCTION__ << "changed powerState to" << itemFromList.powerState();
}

And in a qml screen, I have this code:

Text { text: "equipmentModel.getEquipmentItem(pumpUuid).powerState is " + equipmentModel.getEquipmentItem(pumpUuid).powerState }

This line is NOT reflecting the change made above. Somewhere there's a disconnect between the change, and the QML, but it seems like the model is doing everything correctly.

[JoeCFD]

@mzimmers in my code above you can print out the data value. If it is right, set it. If not, you have to find out the reason.

[mzimmers]

@JoeCFD oh, OK, I got it.

Text { text: "equipmentModel.getEquipmentItem(pumpUuid).powerState is " + equipmentModel.getEquipmentItem(pumpUuid).powerState }

Switch_custom {
    id: sw
    checked: equipmentModel.getEquipmentItem(pumpUuid).powerState === 1
    onClicked: {
        if (switchState === 1) {
            switchState = 0;
        } else {
            switchState = 1;
        }
        equipmentModel.sendSwitchChange(pumpUuid, switchState)
        console.log("Infoscreen.qml: new switch state is " + switchState)
    }
    onVisibleChanged: {
        console.log( "InfoScreen: Switch_custom visible =", visible)
        if (visible) {
            checked = equipmentModel.getEquipmentItem(pumpUuid).powerState === 1
        }
    }
}

The forced update to the checked property of the Switch is working, so the powerState value is good. But the line of text above it (which should reflect the same value) still shows the old value of powerState.

It almost seems that my equipmentItem (the class that the list is composed of) needs to emit a signal when something changes, but my equipmentItem is just a Q_GADGET, so it can't emit signals. In the example, the list item is just a struct, so it's obviously not emitting a signal.

Aargh...

[mzimmers]

Hi all -

Thanks for all the assistance. I'm going to close this topic, even though it's not solved, because I've come to realize that my model is overly complicated, and it make it difficult for me to explain here (there are parts of it that I still don't understand).

So, I'm going to make the following changes to my model:

• use an internal QList instead of using a separate class (currently EquipmentList) for my data list.

• replace the EquipmentItem class with a struct, and eliminate all the now-unnecessary getters and setters.

Hopefully these changes will make it a lot easier to follow what's happening. If I run into trouble, I'll start a new topic...thanks again.