Qt: LNK2001 and LNK2019 Errors occur after implementing a signal / slot in the source files

Question

This consists of declarations in my MainWindow file, I did not include library inclusion for short. I have included QObject.h in both and all the required libraries. It compiles before turning on the second connection call. The first Ctrl-C handler works fine.

I took out my code, thought my employer wouldn't like it. See the appropriate response below!

I am using QT Creator. When I looked for these error messages, most of the solutions provided revolved around fixing the make command / path or something like what happens when compiling in Visual Studio.

I repeat, these errors appeared ONLY after turning on this second call to connect the global GCamera and MainWindow. The program was compiled and executed before that.

Thank you in advance, I apologize for the long post and look forward to receiving any data.

Answer 1

You should have a file called moc_tcamera.cpp that implements the missing character in the assembly directory.

If this is not the case, you should “run qmake” and “Restore” your project (both actions are in the Qt Creator Build menu).

Why the error occurred:

qmake adds moc (Qt meta object compiler) to the Makefile for all source files containing Q_OBJECT or Q_GADGET , such a file is called "mocable". After a file is detected as mosaic or unfocused, this status does not change until qmake is restarted.

QtCreator starts qmake on its own when a .pro file changes (for example, when adding or removing a file).

This means that you probably compiled the project once without the Q_OBJECT macro in the Q_OBJECT file and then added this macro. And since you do not need a meta object until you add a call to connect , VC ++ has not tried to resolve missing characters.

Answer 2

You may get linker errors if you, say, include a header in your .pro file, but not the source. For example, in a .pro file:

 HEADERS += t_camera.h foo.h SOURCES += foo.cpp 

will result in linker errors, usually LNK2001 and LNK2019. However, IIRC QtCreator manages .pro files for you, right? In other words, make sure your .pro file is correct. I would be surprised if this were not the case, but errors in the .pro file may cause the problem you are seeing.