Cannot call `connect` correctly

Question

I'm study C++ Qt. And now try to use lambda function with connect:

connect(ui->sbNormal, &QSpinBox::valueChanged, [=] (int x) {});

It output error:

error: no matching function for call to 'MainWindow::connect(QSpinBox*&, < unresolved overloaded function type>, MainWindow::MainWindow(QWidget*)::< lambda(int)>)'});

What am I do wrong? How to specify needed overloading?

What is the signature of the function you are trying to call? I would guess that it takes a function pointer? — NathanOliver, Mar 28 '16 at 19:47
`void valueChanged(int)` and `void valueChanged(const QString &)`. I need tocall first — Denis Sologub, Mar 28 '16 at 19:48
I don't know... it has a lot of overloads. But this variant works: `connect(sender, &Sender::valueChanged, [=](const QString &newValue) { receiver->updateValue("senderValue", newValue); } );` I got it from Qt docs. — Denis Sologub, Mar 28 '16 at 19:51
Possible duplicate of [Connecting overloaded signals and slots in Qt 5](http://stackoverflow.com/questions/16794695/connecting-overloaded-signals-and-slots-in-qt-5) — Toby Speight, May 18 '16 at 14:57
Possible duplicate of [Qt connect function - signal disambiguation using lambdas](http://stackoverflow.com/questions/26062397/qt-connect-function-signal-disambiguation-using-lambdas) — mpromonet, May 18 '16 at 16:50

score 4 · Accepted Answer · edited Mar 29 '16 at 16:45

4

In case there are multiple overloads, you have to specify which one you want manually:

connect(ui->sbNormal, static_cast<void (QSpinBox::*)(int)>(&QSpinBox::valueChanged),
        [=] (int x) {});

edited Mar 29 '16 at 16:45

Kuba hasn't forgotten Monica

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answered Mar 28 '16 at 19:57

dtech

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Thank you! I found it too) Just I didn't know that C++ can cast function. – Denis Sologub Mar 28 '16 at 19:58

Cannot call `connect` correctly

1 Answers1