How to connect with ButtonGroup clicked(AbstractButton) signal?

[Tom asso]

Documentation says that ButtonGroup emits signal clicked(AbstractButton).

My C++ code:

QObject *obj =
    rootObject->findChild<QObject*>("groupName");
  
QObject::connect((QObject *)obj, 
                SIGNAL(clicked(QAbstractButton)),
                &mainWindow, SLOT(onButtonClicked()));

The code generates an error message:

QObject::connect: No such signal ButtonGroup_QMLTYPE_127::clicked(QAbstractButton)

What am I doing wrong?
Thanks!

[ChrisW67]

The signal sends an AbstractButton not a QAbstractButton.

[Tom asso]

@ChrisW67 - I tried that but get similar error:

QObject::connect((QObject *)obj, 
                SIGNAL(clicked(AbstractButton)),
                &mainWindow, SLOT(onButtonClicked()));

QObject::connect: No such signal ButtonGroup_QMLTYPE_7::clicked(AbstractButton)

[Bonnie]

@Tom-asso What about SIGNAL(clicked(QAbstractButton*)), I mean normally this kind of signal has a pointer as param, not object.
I don't quite know qml, this is just a guess.

And there's a way to check the signals is

obj->dumpObjectInfo();

then look what's printed in the console.

[Tom asso]

@Bonnie - ah, that is a useful function, but I don't understand the signals information it gives. Below is what it says for the ButtonGroup (my QML gives it objectName "editModesObj").
Weird - no info on signal 'clicked()'! What is going on?

OBJECT ButtonGroup_QMLTYPE_124::editModesObj
  SIGNALS OUT
        signal: destroyed(QObject*)
          --> QQuickColumnLayout::unnamed _q_resourceObjectDeleted(QObject*)
  SIGNALS IN
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>
          <-- RadioButton_QMLTYPE_126::unnamed <unknown>

... and my C++ connects successfully to the ButtonGroup's destroyed() signal. My QML also declares a Slider, and my C++ can connect to its valueChanged() signal without problem. But dumpObjectInfo() for the slider does not mention the valueChanged() signal - but a signal "baselineOffsetChanged(double) - now I'm really confused!

OBJECT Slider_QMLTYPE_7::pingStepSliderObj
  SIGNALS OUT
        signal: baselineOffsetChanged(double)
          <functor or function pointer>
          --> QQuickColumnLayout::unnamed invalidateSenderItem()
  SIGNALS IN
          <-- Slider_QMLTYPE_7::pingStepSliderObj <unknown>

[Bonnie]

@Tom-asso Oh, sorry my bad, I thought this function prints all signals, but actually it only prints the signals that already got connected.
You can write code to print the signals though.
Here we start i from meta->methodOffset() so it only prints signals defined in its class, if start from 0, then it will also print signals from superclasses.

const QMetaObject* meta = obj->metaObject();
for (int i = meta->methodOffset(); i < meta->methodCount(); ++i) {
    QMetaMethod method = meta->method(i);
    if(method.methodType() == QMetaMethod::Signal) {
        qDebug() << method.methodSignature();
    }
}

[Sivan]

As @Bonnie mentioned, u are missing * in the signal connection. Its supposed to be

QObject::connect((QObject *)obj, 
               SIGNAL(clicked(QAbstractButton*)),
               &mainWindow, SLOT(onButtonClicked()));

[Pl45m4]

@Sivan said in How to connect with ButtonGroup clicked(AbstractButton) signal?:

As @Bonnie mentioned, u are missing * in the signal connection. Its supposed to be

    QObject::connect((QObject *)obj, 
          SIGNAL(clicked(QAbstractButton*)),
          &mainWindow, SLOT(onButtonClicked()));

What could have been avoided, when using the function pointer based connection style...

Edit:
@Sivan OP is using the QMLs AbstractButton, not QtWidgets QAbstractButton class

[GrecKo]

A cleaner solution would be to expose some of your c++ objects to the QML and call one of its slots from QML when a button is clicked.

Don't connect to QML signals from c++.
https://doc.qt.io/qt-5/qtquick-bestpractices.html#interacting-with-qml-from-c
https://doc.qt.io/qt-6/qtquick-bestpractices.html#exposing-data-from-c-to-qml
https://doc.qt.io/qt-6/qtqml-cppintegration-overview.html#interacting-with-qml-objects-from-c
https://youtu.be/vzs5VPTf4QQ?t=23m20s

[Tom asso]

@GrecKo - yes I'm convinced of that now too.

[Tom asso]

@Bonnie - thanks that's very useful.

[Tom asso]

@Pl45m4 - I didn't know about that function-pointer method; much better to catch errors at compile time!