Connecting problem <unresolved overloaded function type>

[zeroptr]

Hi All,

I use Qsignal mapper in a form for buttons. When I try to connect them I have

error: no matching function for call to 'QPushButton::connect(QPushButton*&, void (QAbstractButton::)(), QSignalMapper&, <unresolved overloaded function type>)'

error: no matching function for call to 'QPushButton::connect(QPushButton*&, void (QAbstractButton::)(), QSignalMapper&, <unresolved overloaded function type>)'
49 | buton->connect(buton, &QPushButton::pressed ,TheMapper, &QSignalMapper::map);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 QList<QPushButton *> widgetlist = this->findChildren<QPushButton  *>();
    foreach (QPushButton *buton, widgetlist) {
        if ((buton->toolTipDuration() > 0) && (buton->toolTipDuration() < 5000))  {
            //buton->connect(buton,SIGNAL(pressed()),TheMapper,SLOT(map()));
            buton->connect(buton, &QPushButton::pressed ,TheMapper, &QSignalMapper::map);
            TheMapper->setMapping(buton,buton->toolTipDuration());
            ObjectMap->insert(buton->toolTipDuration(),buton);
            itemslist->insert(buton->toolTipDuration(),new vitem);
            connect(qobject_cast<vitem*>(itemslist->value(buton->toolTipDuration())),&vitem::boolvaluechanged,
                    buton ,&QPushButton::setFlat);

            //qDebug()<< buton->objectName();
        }

At Qt5 the commented connecting was working.. Any Solution?

[zeroptr]

buton->connect(buton, &QPushButton::pressed ,TheMapper,qOverload<>(&QSignalMapper::map));

solved

[sierdzio]

@zeroptr you probably need to use qOverload to tell connect() which function signature to pick.

[zeroptr]

@sierdzio sorry I couldnot understand the use..

[sierdzio]

The functor-based connection syntax requires providing a pointer to signal and slot in connect call. But if you have overloaded functions, for example:

public slots:
  void doSomething(int i);
  void doSomething(QString i);

then functor syntax is ambiguous: &YouClass::doSomething might mean the integer or QString variant of the method. With qOverload you can specify exactly which method you mean to connect to.

[JonB]

@zeroptr
Did you click on the https://doc.qt.io/qt-6/qoverload-proxy.html#qOverload link @sierdzio gave you? It shows you how to use qOverload() to specify which overload of a method which has multiple signatures you want to use.

There are two possible slots:
void QSignalMapper::map()
void QSignalMapper::map(QObject *sender)
You need to tell C++ which one to use.

[zeroptr]

buton->connect(buton, &QPushButton::pressed ,TheMapper,qOverload<>(&QSignalMapper::map));

solved

[JonB]

@zeroptr
[EDIT: This reply posted before you latest "solved" post.]

Now I'm not sure what you're asking. QOverload(&QSignalMapper::map) simply does not exist, we never said QOverload(...).

I see that https://forum.qt.io/topic/93385/how-to-use-qoverload/4 says qOverload<> may not work on some Windows compilers, so let's use QOverload<>::of().

For your original I would expect

buton->connect(buton, &QPushButton::pressed ,TheMapper, QOverload<>::of(&QSignalMapper::map));

That would pick the overload with no parameters, i.e. void QSignalMapper::map(). The QPushButton::pressed() signal does not pass a QObject *, so you can't call void QSignalMapper::map(QObject *sender).

[hskoglund]

Hi, also consider switching to using lambdas instead of QSignalMapper (which seems to be on it's way out of Qt) say like this:

QList<QPushButton *> widgetlist = this->findChildren<QPushButton  *>();
    foreach (QPushButton *buton, widgetlist) {
        if ((buton->toolTipDuration() > 0) && (buton->toolTipDuration() < 5000))  {
            buton->connect(buton, &QPushButton::pressed, this, [this, buton] { buton->setFlat(true); } );
     
            //qDebug()<< buton->objectName();
        }

Note: haven't tested this :-)

[JonB]

@hskoglund
You are missing parentheses to help the OP get the syntax right:

[this, buton] () { buton->setFlat(true); }

Here you could pass just buton in [...] context, this is not used. Though no harm done, just so the OP knows.

@zeroptr
Absolutely do move over from QSignalMapper to lambdas, much preferable.

[hskoglund]

@JonB the parentheses are optional but I admit to be guilty of that unneeded this :=)

[JonB]

@hskoglund said in Connecting problem <unresolved overloaded function type>:

the parentheses are optional

Wow, really? I never knew that!