Unsolved Accessing C++ object in QML

[StefanoD]

Hi,
I'm trying to access an C++ object in QML by setting a context property via the QQmlApplicationEngine:

main.cpp

ChessModel chessModel;
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty(QStringLiteral("_chessModel"), &chessModel);

Then I try to access it in QML:

main.qml

_chessModel.onInvalidMove: invalidLabel.visible = true
    _chessModel.onValidMove: {
        invalidLabel.visible = false;
        console.log("valid move ", col, row);
    }

But I get a runtime error:
QQmlApplicationEngine failed to load component
qrc:/main.qml:134:5: Cannot assign to non-existent property "_chessModel"

Has anyone an idea why this fails?
My code is publicly available on GitGub.

Thanks in adanvce!

[StefanoD]

I fixed some bugs. Now the property squareSize can't be found although it has been declared directly in QML...

ReferenceError: squareSize is not defined

[dheerendra]

Source code will help us to the right answer.

[RedEx 0]

You can use Connections

Connections {
    target: _chessModel

    //old syntax
    onInvalidMove: {
    }

    onValidMove: {
    }

   //new syntax
   function onInvalidMove(/*params*/) { }
   function onValidMove(/*params*/) { }
}