My second solution would be much more portable.

@JonB the problem is the Meta-Object-Compiler it can't create the magic code to make signal&slots and macros work

you could use Verdigris if you really, really need templated QObject classes

@suslucoder
I'm sorry if you feel I'm being hard on you. Quite a few of your questions are things you really should be able to solve for yourself, not ask questions of other people. It may not seem like it, but in the long run reading documentation and solving things for yourself is the only way to learn. I will leave it at that now.

BTW,

I copied "ui_mainwindow.h" file from another build file

This may or may not be right, depending on just what you did where. The ui_mainwindow.h has to be regenerated every time you edit in Designer to change the mainwindow.ui file. If you later find that you make changes in Designer and these are not reflected in your code, you will have hit a problem. Just saying.

@rhonaldjr

u have marked as solved.
cheers.

Thanks,