Most efficient way to implement data in QML from C++

[sam_s]

Thank you anda_skoa for your help and quick turn around

I'm still really new to Qt and can't find a decent example on how to populate the QAbstractTableModel with row and column data similar to how I was doing it in QML

In this QML code I was able to populate each row with the following code

ListModel{
        id: crcPointListModel
    }
 
    function getDataValues(id)
    {
        var i;
        var j;
 
        for (i = 0; i<23; i++ )
        {
 
            id.set(i,{ "setPoint":crcClassInstance.getDataQML(Global.POINT_SET_POINT,i),
                       "currentValue":crcClassInstance.getDataQML(Global.POINT_CURRENT_VALUE,i),
                       "engineeringUnits":crcClassInstance.getDataQML(Global.POINT_ENGINEERING_UNITS,i),
                       "resolution":crcClassInstance.getDataQML(Global.POINT_RESOLUTION,i),
 
                        name:crcClassInstance.getQMLDataString(Global.POINT_NAME,i),
                       "currentValueSource":crcClassInstance.getDataQML(Global.POINT_CV_ORIGIN,i),
                       "setPointSource":crcClassInstance.getDataQML(Global.POINT_SP_ORIGIN,i),
                       "alarmHigh":crcClassInstance.getDataQML(Global.POINT_ALARM_OVER,i),
                       "alarmLow":crcClassInstance.getDataQML(Global.POINT_ALARM_UNDER,i),
                       "alarmStatus":crcClassInstance.getDataQML(Global.POINT_ALARM_STATUS,i),
                       "displayPoint":crcClassInstance.getBoolDataQML(Global.POINT_DISPLAY,i),
                       "setPointDisplay":false,
                       "alarmSetup":3,
                       "currentValueOffset":crcClassInstance.getDataQML(Global.POINT_CURRENT_VALUE_OFFSET,i)
                   });
        }
    }
 
    Timer{
        id: timerSam
        running: true
        repeat: true
        triggeredOnStart: true
        interval: 1000
        onTriggered: {
            //updates values in c++
            getDataValues(crcPointListModel);
            //sets a value in c++ equal to the current secnd value - just to prove we are able to manipulate values in c++ and see them within the QML delegate
            setIndividualValue(Global.POINT_CURRENT_VALUE, 0, parseInt(Qt.formatTime(new Date(),"ss")) );
 
        }
    }

ListModel{
        id: crcPointListModel
    }

    function getDataValues(id)
    {
        var i;
        var j;
          
        for (i = 0; i<23; i++ )
        {

            id.set(i,{ "setPoint":crcClassInstance.getDataQML(Global.POINT_SET_POINT,i),
                       "currentValue":crcClassInstance.getDataQML(Global.POINT_CURRENT_VALUE,i),
                       "engineeringUnits":crcClassInstance.getDataQML(Global.POINT_ENGINEERING_UNITS,i),
                       "resolution":crcClassInstance.getDataQML(Global.POINT_RESOLUTION,i),

                        name:crcClassInstance.getQMLDataString(Global.POINT_NAME,i),
                       "currentValueSource":crcClassInstance.getDataQML(Global.POINT_CV_ORIGIN,i),
                       "setPointSource":crcClassInstance.getDataQML(Global.POINT_SP_ORIGIN,i),
                       "alarmHigh":crcClassInstance.getDataQML(Global.POINT_ALARM_OVER,i),
                       "alarmLow":crcClassInstance.getDataQML(Global.POINT_ALARM_UNDER,i),
                       "alarmStatus":crcClassInstance.getDataQML(Global.POINT_ALARM_STATUS,i),
                       "displayPoint":crcClassInstance.getBoolDataQML(Global.POINT_DISPLAY,i),
                       "setPointDisplay":false,
                       "alarmSetup":3,
                       "currentValueOffset":crcClassInstance.getDataQML(Global.POINT_CURRENT_VALUE_OFFSET,i)
                   });
        }
    }

    Timer{
        id: timerSam
        running: true
        repeat: true
        triggeredOnStart: true
        interval: 1000
        onTriggered: {
            //updates values in c++
            getDataValues(crcPointListModel);
            //sets a value in c++ equal to the current secnd value - just to prove we are able to manipulate values in c++ and see them within the QML delegate
            setIndividualValue(Global.POINT_CURRENT_VALUE, 0, parseInt(Qt.formatTime(new Date(),"ss")) );

        }
    }

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Here are my questions:
- Does the QAbstractListModel have its own built in model / container?
- If it doesn't have its own container - given the model that this would have to replace in the QML code above - what would be the best container? QVector <QObject> ?
- If using QAbstractmodel is the best approach, then does every column need it's own get set function or can I populate each row with column / data as I was able to above?

Any direction or examples would help out greatly.

Thank you again for your help!

[anda_skoa]

- Does the QAbstractListModel have its own built in model / container?

No, it is just an interface to the data.
Your implementation can hold the data or delegate to a class that holds the data.
Your "crcClassInstances" sounds like you already have the latter.

- If it doesn't have its own container - given the model that this would have to replace in the QML code above - what would be the best container? QVector <QObject> ?

QVector sounds good, but as the element type you can use any data specific class you want.
Again your code looks like you already have the data stored somewhere.

- If using QAbstractmodel is the best approach, then does every column need it's own get set function or can I populate each row with column / data as I was able to above?

No. All data is accessed through the model's data() function.
In QML each delegate just accesses its data by the role names for each data aspect/column.

Any direction or examples would help out greatly.

I found a couple by googling for "c++ models for QML":
http://doc.qt.io/qt-5/qtquick-modelv...model-subclass
https://sailfishos.org/develop/tutor...ng-c-with-qml/

Creating such a model is fairly easy
1) Create a class derived from QAbstractListModel
2) Add an enum for the data roles
3) Implement roleNames() to provide a mapping between these enum values and the role names to use on QML side
4) Implement rowCount() to return the number of rows you have data for
5) Implement data() to return the value for a given row (from the index argument) and role (from the role argument)

Cheers,
_