Getting errors when using Qt Creator to create sig

Question

I've created a new dialog using Qt Creator (version 4.7.0) - one of the templated forms (with an OK and a Cancel button).

I want the user to enter some data on the form and then when they click OK, it saves that information. So I had a look, and saw that when the OK button is clicked, it sends and signal to the dialog's accept slot.

So I right clicked on the dialog in the design view, and selected "Go to slot...". I clicked on the "accepted" option, which dropped an on_Dialog_accepted() method into the dialogs class. However, when I run the program and open the dialog, I get an error in my console saying QMetaObject::connectSlotsByName: No matching signal for on_Dialog_accepted()

So what did I do wrong?

I've found documentation on the connectSlotsByName - but nothing about any obvious pratfalls that an inexperienced Qt-developer can get themselves into.

Answer 1

It is basically just as Fred explained: you did not do anything wrong. This is a QtCreator bug. And a pretty old one for that matter. Unfortunately, even two years later nothing in that regard has changed.

The assignee of the aforementioned bug decided to sort of redirect it to this QtCore bug, which simply asks for QMetaObject::connectSlotsByName() to be changed in a way that it also processes the passed object and not only its children (thereby fixing the QtCreator issue).

I had a look at the source and submitted a trivial patch.

Update: The patch got accepted, meaning this bug is going to be fixed in Qt 5.1. Note: it is not relevant which version of QtCreator your are using but which version of Qt you link your code to.

Answer 2

Right-clicking on the dialog in the design view prior to selecting "Go to slot..." made a connection from the dialog's signals to the dialog's slot, which doesn't work with QMetaObject::connectSlotsByName(), since that method searches for all child objects, but not for the object itself.

What you wanted to do actually is right-clicking on the OK button, then selecting "Go to slot..." from there. It will then create a slot with the name of your button widget, and the connection will be made correctly at run-time.

It makes no sense that QtDesigner lets you select "Go to slot..." from the Dialog. You might want to file a bug to Qt's devs for that.