Calling multiple UI's?

[ChrisW67]

This is a compilation error telling you quite plainly that "adressViewer" is not declared before you try to use it. If the compiler cannot find a definition, is it any wonder that the IDE (Qt Creator I assume) cannot either. With the limited information you have provided, the only obvious things to check are:

• That the "ui_adresses.h" file is generated, carries the correct name, and actually declares a class "adressViewer" (not "adresses"). This name is definitely not the default name that Qt Creator would have generated for you (that would have been ui_adressviewer.h).
• That you have not "accidentally" spelt the word "address" correctly in your declaration and incorrectly everywhere else.

The dot is not a shortcut in C++ for pointer dereferencing. Qt Creator corrects the common error of trying to use a dot to access a class member through a pointer. It can only do this if it knows what type things are: not the case here.