C++ can't find ButtonGroup?

Tom asso

I'm running Qt 5.15.
My C++ app cannot find a ButtonGroup declared with an objectName in QML. The radio buttons in the group appear to function properly and the C++ app is able to find all other objectNames in QML, but not the one for ButtonGroup.

main.qml:

ButtonGroup {
      id: editModes
      objectName: "editModesObj"
    }

    Row {
       id: buttonRow
       
        RadioButton {
          checked: true
          text: qsTr("Male")
          ButtonGroup.group: editModes
         }

        RadioButton {
          text: qsTr("Female")
          ButtonGroup.group: editModes    
        }

main.cpp:

#define EDIT_MODES_NAME “editModesObj”

QButtonGroup *obj =
      rootObject->findChild<QButtonGroup*>(EDIT_MODES_NAME);

if (!obj) {
      qWarning() << "Couldn't find QML object named " << EDIT_MODES_NAME;
}

The result of the above call to findChild() is null for "editModesObj". What am I doing wrong? Should I expect a non-visual object like ButtonGroup to be find-able by findChild()? If not, how can my C++ connect the ButtonGroup signal to a slot?
Thanks!

ChrisW67

I suspect that the ButtonGroup QML object expose a QObject interface, not a QButtonGroup

QObject *obj =
      rootObject->findChild<QObject*>(EDIT_MODES_NAME);

Read the warning here though.

Read here to understand how QML signals are automatically available in C++.

Tom asso

@ChrisW67

| I suspect that the ButtonGroup QML object expose a QObject | |
| interface, not a QButtonGroup

Yes, findChild<QObject*> finds the ButtonGroup!
Brilliant! How in the world did you know that?
Regarding the Warning about 'manipulating' QML from C++, my C++ code is only establishing a slot for the ButtonGroup signal, which seems a pretty standard way to do things in the Qt world.

ChrisW67

@Tom-asso said in C++ can't find ButtonGroup?:

Brilliant! How in the world did you know that?

The example immediately above the warning.

Regarding the Warning about 'manipulating' QML from C++, my C++ code is only establishing a slot for the ButtonGroup signal, which seems a pretty standard way to do things in the Qt world.

Yes. Using the standard QObject mechanisms is OK. Doing something like this (from a little further down the same page) is not:

//bad code
QQmlComponent component(engine, "MyButton.qml");
PushButton *button = qobject_cast<PushButton*>(component.create());
button->m_buttonText = "Click me";