QT how to emit a signal in this case - c++

Question

I need to develop a Sudoku game. After reading a text file containing the number values, I create 9*9 widgets.
If (the value is already set then I instantiate to a qlabel containing the number,
else I instantiate a combobox containing the possible values of each case).
Until here everything is OK.
The problem is that when a value is chosen from the combobox, I need to draw it in a square in my view (MVC). The problem is how can I know which one was chosen?
The only signal can I use from combobox signals is currenttextchanged(QString), but I'll not know which combo made that signal.
The ideal for me would be something like this SIGNAL(curretextchanged(QString, int, int)), but I don't know if I can define a new signal?
Here is some code:
QWidget *tab[9][9];
SudModel *modele = ???;
QComboBox *combobox = new QComboBox();
combobox->setStyleSheet("border: 1px solid red");
int tmp = modele->valuesof(i, j).size();
for (int s = 0; s < tmp; s++) {
combobox->addItem(QString::number(modele->valuesof(i, j)[s]));
}
connect(combobox, SIGNAL(currentTextChanged(QString)), this, SLOT(update()));
tab[i][j] = combobox;

Answer 1

One solution would be to attach that extra information when you connect to the signal for a specific combobox.
For example, say you have your function update(QString text, int x, int y) then you could attach the signal to a lambda that calls the function with the extra arguments, captured at connect time. Something like this:
connect(combobox, &QComboBox::currentTextChanged, [x, y, this](const QString& text){ this->update(text, x, y); });
That would then call the update functions with the x and y values captured when the connection was made along with the text argument that originated from the signal.

Answer 2

You can ask the slot for a sender()
QObject *QObject::sender() const
Returns a pointer to the object that sent the signal, if called in a
slot activated by a signal; otherwise it returns 0. The pointer is
valid only during the execution of the slot that calls this
function from this object's thread context.

Answer 3

You can use QSignalMapper.
In this you map every item with mapper with any specific string. Now when any mapped item emits signal you can know which item emitted it by the string.
You can use the same with minor changes like using Signal 'currentTextChanged' as mentioned. But the same result can be obtained by using 'currentIndexChanged' signal with some modifications.
signalMapper = new QSignalMapper(this);
for (int i = 0; i < 2; ++i) {
QComboBox *combo = new QComboBox();
connect(combo, SIGNAL(currentIndexChanged()), signalMapper, SLOT(map()));
signalMapper->setMapping(combo, "combo" + i);
}
connect(signalMapper, SIGNAL(mapped(QString)),
this, SIGNAL(indexChanged(QString)));
NOTE : (source Qt Assistant)
QSignalMapper class collects a set of parameterless signals, and
re-emits them with integer, string or widget parameters corresponding
to the object that sent the signal