QT Looking for Signal in parent class, rather than derived class.

Smeeth

I have a ButtonPanel widget that I use as a base widget for a couple of different ButtonPanels with different configuration.

In each derived class, I am trying to connect signals for that particular class, but when I try to connect the signals, I get an error:

QObject::connect: No such signal ButtonPanel::mostRecentPatientBtn_Clicked() in ..welcomebuttonpanel.cpp:6

So it seems QT is looking for the signal in ButtonPanel, the parent class, and not finding the signal in WelcomeButtonPanel, the derived class.

The base class is ButtonPanel:

Header:

#ifndef BUTTONPANEL_H
#define BUTTONPANEL_H

#include <QPushButton>
#include <QVBoxLayout>
#include "customwidget.h"

class ButtonPanel : public CustomWidget
{
    Q_OBJECT
public:
    explicit ButtonPanel(QWidget *parent = nullptr);

signals:

public slots:
};

#endif // BUTTONPANEL_H

Source:

#include "buttonpanel.h"
#include "uiutils.h"

ButtonPanel::ButtonPanel(QWidget *parent) : CustomWidget(parent)
{

    this->setStyleSheet("QPushButton {font: bold 22px 'Arial'; color: white; background-color: navy;"
                        "border: 3px solid #232323;"
                        "border-radius: 15px;}"
                        "QPushButton#powerOffBtn {background: red;}");

  //other unrelated code here

}

The derived class is WelcomeButtonPanel:

Header

#ifndef WELCOMEBUTTONPANEL_H
#define WELCOMEBUTTONPANEL_H

#include "buttonpanel.h"

class WelcomeButtonPanel : public ButtonPanel
{
public:
    WelcomeButtonPanel();

signals:
    void mostRecentPatientBtn_Clicked();
    void newPatientBtn_Clicked();
    void managePatientsBtn_Clicked();
    void settingsBtn_Clicked();
    void powerOffBtn_Clicked();

private:
};

#endif // WELCOMEBUTTONPANEL_H

Source:

#include "welcomebuttonpanel.h"

WelcomeButtonPanel::WelcomeButtonPanel()
{
    QPushButton *mostRecentPatientBtn = new QPushButton("Most Recent\nPatient");
    connect(mostRecentPatientBtn, SIGNAL(clicked()), this, SIGNAL(mostRecentPatientBtn_Clicked()));
    QPushButton *newPatientBtn = new QPushButton("New\nPatient");
    connect(newPatientBtn, SIGNAL(clicked()), this, SIGNAL(newPatientBtn_Clicked()));
    QPushButton *managePatientsBtn = new QPushButton("Manage\nPatients");
    connect(managePatientsBtn, SIGNAL(clicked()), this, SIGNAL(managePatientsBtn_Clicked()));
    QPushButton *settingsBtn = new QPushButton("Settings");
    connect(settingsBtn, SIGNAL(clicked()), this, SIGNAL(settingsBtn_Clicked()));
    QPushButton *emptyBtn = new QPushButton;
    QPushButton *powerOffBtn = new  QPushButton("Power\nOff");
    connect(powerOffBtn, SIGNAL(clicked()), this, SIGNAL(powerOffBtn_Clicked()));

    mostRecentPatientBtn->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    newPatientBtn->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    managePatientsBtn->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    settingsBtn->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    emptyBtn->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    powerOffBtn->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);

    QVBoxLayout *layout = new QVBoxLayout;
    layout->setMargin(15);
    layout->setSpacing(15);
    layout->addWidget(mostRecentPatientBtn, 1);
    layout->addWidget(newPatientBtn, 1);
    layout->addWidget(managePatientsBtn, 1);
    layout->addWidget(settingsBtn, 1);
    layout->addWidget(emptyBtn, 1);
    layout->addWidget(powerOffBtn, 1);

    emptyBtn->hide();

    this->setLayout(layout);
}

In this code, I try to connect each button clicked signal to a WelcomeButtonPanel signal as described here. However, I get errors on all the lines that try to connect the slots with No such signal ButtonPanel::mostrecentPatientBtn_Clicked(), so it is obviously not finding the slot in WelcomeButtonPanel.

How can I fix this issue?

SGaist

Hi,

First thing I can see is that you are missing the Q_OBJECT macro in your class.

Don’t forget to re-run qmake after adding it and before building your application.

Smeeth

@SGaist facepalm Well, you were right. I included it in the base class, where I didn't need it, and not in the derived class, where I do need it, and ended up reading too far into the error message to realize.

Thank you!