Send parameters with dynamically generated QComboBox - c++

Question

I want to insert a QComboBox inside a QTableWidget. When I change the Index of the CB I'll call a methode to change the status in the sqlite table. But for this, I need do pass two parameters to the methode. The ID(First element of the row), and the current index of the CB.
I generate the QTableWidget like that:
...
for(int i = 0; i < dbModel->rowCount();i++){
row = dbModel->record(i);
ui->tW_Services->setItem(i,0,new QTableWidgetItem(row.field(0).value().toString()));
ui->tW_Services->setItem(i,1,new QTableWidgetItem(row.field(1).value().toString()));
ui->tW_Services->setItem(i,2,new QTableWidgetItem(row.field(2).value().toString()));
ui->tW_Services->setItem(i,3,new QTableWidgetItem(row.field(3).value().toString()));
ui->tW_Services->setItem(i,4,new QTableWidgetItem(row.field(4).value().toString() + "€"));
ui->tW_Services->setItem(i,5,new QTableWidgetItem(row.field(5).value().toString() + "€"));
//ui->tW_Services->setItem(i,6,new QTableWidgetItem(row.field(6).value().toString()));
QComboBox* combo = new QComboBox();
combo->addItem("open");
combo->addItem("paid");
if(row.field(6).value().toString() != "paid") combo->setCurrentIndex(0);
else combo->setCurrentIndex(1);
connect(combo, SIGNAL(currentIndexChanged(int)), this, SLOT(onComboChanged(int)));
ui->tW_Services->setCellWidget(i,6,combo);
}
...
and the slot looks like that:
void MainWindow::onComboChanged(int ID)
{
qDebug() << "ID:" << QString::number(ID);
}
But when I try to create the method with 2 args:
void MainWindow::onComboChanged(int ID,int index)
{
qDebug() << "ID:" << QString::number(ID);
}
and attach a second parameter and calling the slot like:
connect(combo, SIGNAL(currentIndexChanged(int)), this, SLOT(onComboChanged(row.field(0).value().toInt(),int)));
I get:
qt.core.qobject.connect: QObject::connect: No such slot MainWindow::onComboChanged(row.field(0).value().toInt(),int)
A minimal reproducible example:
There's just a single pushbutton and a qtablewidget
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void on_pushButton_clicked();
void onComboChanged(int ID, int index);
void onComboChanged2(int index);
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QComboBox>
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
ui->tableWidget->setColumnCount(4);
ui->tableWidget->setRowCount(3);
for(int i = 0; i < 3;i++){
ui->tableWidget->setItem(i,0,new QTableWidgetItem(QString::number(i)));
ui->tableWidget->setItem(i,1,new QTableWidgetItem("Test"));
ui->tableWidget->setItem(i,2,new QTableWidgetItem("Test 2"));
QComboBox* combo = new QComboBox();
combo->addItem("open");
combo->addItem("paid");
combo->setCurrentIndex(0);
int j = i+1;
//NOT WORKING
//connect(combo, SIGNAL(currentIndexChanged(int)),this,
// [=](int index) {this->onComboChanged(j, index);});
//WORKING
//connect(combo, SIGNAL(currentIndexChanged(int)),SLOT(onComboChanged2(int)));
ui->tableWidget->setCellWidget(i,3,combo);
}
}
void MainWindow::onComboChanged(int ID, int index)
{
qDebug() << "ID: " << ID << "index: "<< index;
}
void MainWindow::onComboChanged2(int index)
{
qDebug() << "ID: " << index;
}

Answer 1

Since currentIndexChanged only has one parameter, your slot cannot capture more than that. But, since the row ID does not change on emission, you can wrap onComboChanged into a lambda as shown here, which captures the row by copy:
connect(combo, &QComboBox::currentIndexChanged,
this, [=](int index) {this->onComboChanged(i, index);});
Since your code is not a minimal reproducible example, I could not test this. Let me know, if it doesn't work.