Quote Originally Posted by wysota View Post
If you didn't define it in a separate file that you didn't post here then I believe the constructor is not defined, only declared. And based on the project file that you posted I believe main.cpp is your only C++ file (apart qmlapplicationviewer) thus I believe there are no other files in your project where you might have defined the constructor. This is basic C++ stuff, nothing Qt related.
Thank you so much for your help. I'll follow your instruction.