I want to connect to windows in QT.

I know how to connect two widgets in same window.

`using QObject::connect()` in `ui_a.h`;

But now, I have two windows.

Six files.

For example:

`ui_a.h`(Window A)

`a.h` `a.cpp` (`Widget` in window A)

`ui_b.h`(Window B)

`b.h` `b.cpp` (`Widget` in window B)

How to connect two widget which are in different windows?

Thank you.