QML QT backend and GUI design - doesn't update the object - c++

Question

I have simple object with collection which is created and managed under C++ code and I want to let user view it and modify it from GUI (QML - presentation of the collection and add/remove commands), but lifetime and business logic should be managed by backend (C++)
class QtModel : public QAbstractListModel {
Q_OBJECT
public:
explicit QtModel(QObject *parent = nullptr);
int rowCount(const QModelIndex &parent = QModelIndex()) const override;
QVariant data(const QModelIndex &index,
int role = Qt::DisplayRole) const override;
QHash<int, QByteArray> roleNames() const override;
void test();
private:
std::vector<std::shared_ptr<Data>> collection_;
};
where test method push a new element:
void QtModel::test(){
collection_.push_back(std::make_shared<Data>("test"));
}
I tried follow this way:
https://doc.qt.io/qt-5/qtqml-cppintegration-contextproperties.html
And qml code just takes the current state of the object. The further modifications are ignored:
application = std::make_unique<QGuiApplication>((int &)argc, argv);
engine = std::make_shared<QQmlApplicationEngine>();
qt_model_.test(); // 1 element, GUI shows 1 element
engine->rootContext()->setContextProperty("myGlobalObject", &qt_model_);
// those are ignored
qt_model_.test(); // 2 elements, GUI shows 1 element
qt_model_.test(); // 3 elements, GUI shows 1 element
qt_model_.test(); // 4 elements, GUI shows 1 element
application->exec();
For presentation I am using GridLayout like this:
GridLayout {
anchors.fill: parent
flow: width > height ? GridLayout.LeftToRight : GridLayout.TopToBottom
Repeater {
model: myGlobalObject
delegate : Rectangle {
Layout.fillWidth: true
Layout.fillHeight: true
color: Style.appLightBackgroundColor
Label {
anchors.centerIn: parent
text: model.name
color: Style.fontDarkColor
}
}
}
}
So the object in QML is not updated, while the modifications are taken place after its registration in C++

Answer 1

You are not sending RowsInserted signals from the test function, so QML cannot know when to update. Please adjust like so:
void QtModel::test(){
beginInsertRows({}, collection_.size(), collection_.size() + 1);
collection_.push_back(std::make_shared<Data>("test"));
endInsertRows();
}