Passing overloaded pointer to member function signal as an argument to QObject::connect

Question

In Qt if the signal is not overloaded it can be passed to the connect method like this.

QObject::connect(comboBox, &QComboBox::currentTextChanged, [&]()-> void {});

But if the signal is overloaded then it can be done in two steps.

Example:

In Qt's QComboBox class the highlighted method is overloaded

void QComboBox::highlighted(int index)
void QComboBox::highlighted(const QString & text)

When using the QObject::connect we can declare the pointer to member function variable and then use it which requires 2 steps.

       void (QComboBox::*fptr) (int) = &QComboBox::highlighted;
            QObject::connect(comboBox, fptr, [&]()-> void {
                                 insertWidgetToMapAndSend(listView);
                             });

Is it possible to pass the overloaded method without the declaration of ftptr ?

score 6 · Accepted Answer · answered Jun 12 '18 at 06:48

You can cast inline:

QObject::connect(comboBox, static_cast<void (QComboBox::*)(int)>(&QComboBox::highlighted), [&]()-> void {
                             insertWidgetToMapAndSend(listView);
                         });

But starting with Qt 5.7, use qOverload:

QObject::connect(comboBox, qOverload<int>(&QComboBox::highlighted), [&]()-> void {
                             insertWidgetToMapAndSend(listView);
                         });

or QOverload in pre C++14:

QObject::connect(comboBox, QOverload<int>::of(&QComboBox::highlighted), [&]()-> void {
                             insertWidgetToMapAndSend(listView);
                         });

That's the proper way to do it, and indeed `qOverload` and `QOverload` are preferred over the `static_cast`: they are less verbose. — Kuba hasn't forgotten Monica, Jun 12 '18 at 06:55

Passing overloaded pointer to member function signal as an argument to QObject::connect

Example:

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