Problems signalling from QML to C++

[Willem Ferguson]

Dear Dirk, Sebastian,

If it were possible to have feedback from you based on not more than 15 
minutes of your time, I would greatly appreciate it. I am trying to get 
the QML to signal to the C++ and, due to newby inexperience, I am 
totally stuck. I address a number of issues here, but the first one is 
the substantive one, the others are small. I take the liberty of 
attaching the code in three files.

1) Signalling from the Continue button in the QML to the appropriate C++ 
slot. I use an approach as close as possible to that of QmlManager in 
Subsurface-mobile. I create a message object with a slot, and connect 
this to the QML signal. Using QtCreator I get a compile-time error:
/home/willem/qml/vendor/main.cpp:48: error: undefined reference to 
`GUIMessageClass::~GUIMessageClass()'
There is a possibility this is a systemic problem related to the way of 
presenting code to QTCreator, but I am too naïve to be able to determine 
this. Any comment at all will be invaluable.

2) In the object in the header file, what does ~MessageClass mean? It 
eliminates a compilation error for this code.

3) With respect to the two models used in the QML, I get warnings from 
the QML debugger in QtCreator:

qrc:main.qml:24: ReferenceError: vendorModel is not defined

qrc:main.qml:35: ReferenceError: productModel is not defined

qrc:main.qml:35: ReferenceError: productModel is not defined

These warnings do not cause faulty execution, though. But I would love 
to know how they arise.

4) When running the code within QtCreator, the combo boxes do not work 
well. They need to be clicked several times before the options are 
shown. However, if I provide models inside of QML (i.e. not using a C++ 
external source) and I run the code using qmlscene, then the combo boxes 
work as expected. So, FOR THE MOMENT I assume it is a problem in the way 
QtCreator does the QML interpretation and that the QML is likely to run 
as expected on a mobile device.
Kind regards,
willem

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