QQmlPropertyMap, Unable to assign [undefined] to ....

adaptine

Hello

I'm populating a QQmlPropertyMap dynamically;

m_propertyMap.insert(node.key(), 0);

The value is updated in an other function (nodeValueUpdate) connected to a signal "dataChangeOccured";

QObject::connect(m_nodes.value(node.key()).data(), &QOpcUaNode::dataChangeOccurred,
                    [=](QOpcUa::NodeAttribute attr, QVariant value) { nodeValueUpdate(attr, value, node.key()); });

void opcClient::nodeValueUpdate(QOpcUa::NodeAttribute attr, const QVariant &value, const QString &key)
{
    Q_UNUSED(attr);

    QByteArray key_ba = key.toLatin1();
    const char *key_ch = key_ba.data();
    if (m_propertyMap.contains(key_ch))
        m_propertyMap.insert(key_ch, value);
}

In main.cpp, the propertymap is made available to QML:

engine.rootContext()->setContextProperty("opcMap", opcclient.getPropertyMap());

I can then access the properties loaded in the constructor in said class with "opcMap.PropertyKeyHere".
My problem is that I'm getting errors/warnings saying "Unable to assign [undefined] to bool, double, QString" etc... The data is displayed correctly in my program tho. How to fix this?

sierdzio

Maybe you assign the values before m_propertyMap is populated with values? Can you narrow the warnings down to a single line or component of QML code and show it to us?

adaptine

The "flow" goes like this starting in the constructor of my class:

myClass Constructor called: Load and parse external node-configuration for property map, register qml type, call myClass::connectToEndpoint
myClass::connectToEndpoint: create the opcua client, connect QOpcUaClient::stateChanged to myClass::clientStateHandler, call QOpcUaClient::connectToEndPoint which'll presumably cause myClass::clientStateHandler to be called due to QOpcUaClient::stateChanged-signal.
myClass::clientStateHandler: if connected, iterate the node-map loaded in constructor and populate the property-map, connect QOpcUaNode::dataChangeOccured to myClass::nodeValueUpdate (as in first post), subscribe to data changes on opcua server
myClass::nodeValueUpdate as shown in first post.

Example from QML:

        Tank {
            id: tank1
69            name: opcMap.tank1Title

78            volumeMaxValue: opcMap.tank1MaxVol
79            heightMaxValue: opcMap.tank1MaxHeight
80            volumeValue: opcMap.tank1Vol
81            heightValue: opcMap.tank1Height
 .            topFieldEn: true
 .            lowAlarmEn: opcMap.tank1MinAlarmEn
            highAlarmEn: opcMap.tank1MaxAlarmEn
            alarm: opcMap.tank1MinAlarm || opcMap.tank1MaxAlarm
            lowAlarm: opcMap.tank1MinAlarmLim
            highAlarm: opcMap.tank1HighAlarmLim
            relativeValue: opcMap.tank1RelVal
        }

Gives:

qrc:/Ballast.qml:88:13: Unable to assign [undefined] to double
qrc:/Ballast.qml:87:13: Unable to assign [undefined] to double
qrc:/Ballast.qml:86:13: Unable to assign [undefined] to double
qrc:/Ballast.qml:85:13: Unable to assign [undefined] to bool
qrc:/Ballast.qml:84:13: Unable to assign [undefined] to bool
qrc:/Ballast.qml:83:13: Unable to assign [undefined] to bool
qrc:/Ballast.qml:81:13: Unable to assign [undefined] to double
qrc:/Ballast.qml:80:13: Unable to assign [undefined] to double
qrc:/Ballast.qml:79:13: Unable to assign [undefined] to double
qrc:/Ballast.qml:78:13: Unable to assign [undefined] to double
qrc:/Ballast.qml:69:13: Unable to assign [undefined] to QString

As you can see, this is currently read only.

I tried adding just a simple qDebug() to print some random stuff inside the while-loop that's adding the nodes to the property map and the "Unable to assign" errors appears in the application output before my qDebug-print outs!

So I somehow must delay the creation of the QML-part untill after the property map has been created?
How can I do this? Perhaps I can create some sort of a splash screen to display "current status" and possible error messages.

Bear with me, I'm a newbie to Qt...

sierdzio

QML code is initialized when you call setSource on QML engine. If you don't have your data ready then, there are several options:

first, make sure you register the QML type before you call setSource
initialize your map with zeroes or some empty values while you wait for real data
or use Loader component to load your Tank objects only after your map is ready
or use Binding element to only set values in QML if some condition is met