QT6 - signal/slot between 2 classes - c++

Question

I have created a new class for qpushbutton, I am trying to establish signal slot communication between this class and my mainwindow class
connect(&MyPushButton, &pushbutton::pb_isChecked, this, &MainWindow::MainWindowPBClicked, Qt::DirectConnection);
I used this code but as output only
qDebug("pushButtonClicked");
I can get this output. After that, the slot I called with "emit" does not work.
void pushbutton::pushButtonClicked()
{
if (isChecked())
{
qDebug("pushButtonClicked");
**emit pb_isChecked();**
}
}
all code in my project;
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MainWindow ui;
ui.show();
return app.exec();
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QDebug>
#include "pushbutton.h"
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
public slots:
void MainWindowPBClicked();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
pushbutton MyPushButton;
connect(&MyPushButton, &pushbutton::pb_isChecked, this, &MainWindow::MainWindowPBClicked, Qt::DirectConnection);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::MainWindowPBClicked()
{
qDebug("MainWindowPBClicked");
}
pushbutton.h
#ifndef PUSHBUTTON_H
#define PUSHBUTTON_H
#include <QWidget>
#include <QPushButton>
class pushbutton : public QPushButton
{
Q_OBJECT
public:
explicit pushbutton(QWidget *parent = nullptr);
public slots:
void pushButtonClicked();
signals:
void pb_isChecked();
};
#endif // PUSHBUTTON_H
pushbutton.cpp
#include "pushbutton.h"
#include "mainwindow.h"
pushbutton::pushbutton(QWidget *parent)
: QPushButton{parent}
{
setAcceptDrops(true);
connect(this, &QPushButton::clicked, [this]() {
pushButtonClicked();
});
}
void pushbutton::pushButtonClicked()
{
if (isChecked())
{
qDebug("pushButtonClicked");
emit pb_isChecked();
}
}

Answer 1

CASE 1: Not creating button in UI file:
In your class MainWindow, variable MyPushButton is a local variable that gets destroyed after it end its scope in constructor. You need to create a dynamic variable of pushButton like this:
pushbutton *MyPushButton = new pushButton(this);
connect(MyPushButton, SIGNAL(pb_isChecked()), this, SLOT(MainWindowPBClicked()), Qt::DirectConnection);
CASE 2: Creating button in UI file:
In this case you cannot use your custom signal pb_isChecked(). You will need to use standard QPushButton signal such as clicked()
connect(ui->MyPushButton, SIGNAL(clicked()), this, SLOT(MainWindowPBClicked()), Qt::DirectConnection);