Connect with derived class

nefarious

I have a base class:

class QCcmStatusPanel  : public QFrame
{
    Q_OBJECT
public:
    explicit QCcmStatusPanel(QWidget *parent = 0);
    ~QCcmStatusPanel();

private:
    QOverflowCtrl* mOverflowCtrl;

public slots:
    void OverflowSlot(int overflow);
};

and a derived class

class QCcmTimeDomainStatusPanel
        : public QCcmStatusPanel
{
public:
    QCcmTimeDomainStatusPanel(QWidget *parent = 0);
    ~QCcmTimeDomainStatusPanel();

private:
    QDistributorDepthCtrl* mDistributorDepthCtrl;

public slots:
    void DistributorDepthSlot(int distributorDepth);
};

in my application I instantiate the class as

    mStatusPanel = new QCcmTimeDomainStatusPanel(this);
    connect(distributor, SIGNAL(SetDepthSignal(int)),
            mStatusPanel, SLOT(DistributorDepthSlot(int)));

and I get a message
QObject::connect: No such slot QCcmStatusPanel::DistributorDepthSlot(int)
complaining that the base class doesn't have the slot that is defined in the base class.

Is there something I have to do in connect for this to work?

Hi! Whenever you use signals and slots in a class you need to add the Q_OBJECT.

jsulm

@nefarious mStatusPanel is a QCcmStatusPanel, right? Since QCcmStatusPanel does not have DistributorDepthSlot slot you get that error. You need to cast the pointer mStatusPanel to QCcmTimeDomainStatusPanel* in the connect call (http://doc.qt.io/qt-5.7/qobject.html#qobject_cast).

Buckwheat

@jsulm where are you seeing the code for your comment??? I agree with @Wieland that the Q_OBJECT needs to be in QCcmTimeDomainStatusPanel.

jsulm

@Buckwheat In @nefarious first post

mrjj

Hi
If i put his code in a .h file I get
"Error: Class declaration lacks Q_OBJECT macro."
for QCcmTimeDomainStatusPanel
(mingw compiler)

Buckwheat

@jsulm ... I still don't see the declaration for mStatusPanel. I think it is being assumed in the argument. I am not saying you are wrong on the intended declaration but I still believe the problem is the missing Q_OBJECT.

jsulm

@Buckwheat My assumption is based on the error message:

QObject::connect: No such slot QCcmStatusPanel::DistributorDepthSlot(int)

Buckwheat

@jsulm ... so was mine and @Wieland. But I use SIGNAL()/SLOT() (older method) with base classes all the time without issue unless I forget my Q_OBJECT or Q_GADGET.