Grid of QComboBox

[yeye_olive]

Here we go for the second approach (subclass QComboBox). I recommend the first approach (QSignalMapper), though.

Disclaimer: I did not even try to compile this code, there may be errors.

class MyComboBox : public QComboBox {
Q_OBJECT
public:
    MyComboBox(int id, QWidget *parent = 0);
signals:
    void currentIndexChanged(int index, int id);
protected slots:
    void onCurrentIndexChanged(int index);
protected:
    int m_id;
};
 
MyComboBox::MyComboBox(int id, QWidget *parent) : QComboBox(parent), m_id(id) {
    connect(this, SIGNAL(currentIndexChanged(int)), SLOT(onCurrentIndexChanged(int)));
}
 
void MyComboBox::onCurrentIndexChanged(int index) {
    emit currentIndexChanged(index, m_id);
}

class MyComboBox : public QComboBox {
Q_OBJECT
public:
    MyComboBox(int id, QWidget *parent = 0);
signals:
    void currentIndexChanged(int index, int id);
protected slots:
    void onCurrentIndexChanged(int index);
protected:
    int m_id;
};

MyComboBox::MyComboBox(int id, QWidget *parent) : QComboBox(parent), m_id(id) {
    connect(this, SIGNAL(currentIndexChanged(int)), SLOT(onCurrentIndexChanged(int)));
}

void MyComboBox::onCurrentIndexChanged(int index) {
    emit currentIndexChanged(index, m_id);
}

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Signals are not simple methods (although they are implemented by moc as methods). They are emitted by a component and you need to connect them to a slot to react to their emission.

[ZikO]

Thanks for this. I can see that your connect function has only three arguments whereas it should have 4: Widget, SIGNAL, Widget, SLOT ? Should there be this in the middle, as the third parameter?

[yeye_olive]

That is because I used the QObject::connect() non-static method, which is indeed equivalent to using the static one with "this" between the signal and the slot parameters.