In the adressbook.cpp file you should also use:

#include <QLineEdit>

Google for Forward declaration to understand why.

Please add @ code tags on your code. See the button with <> on it on top of the editor here.

You must include QLineEdit and other which you use

Edit:
As Eddy says. I’m late little bit :)

It is spelled QLineEdit, not QLineEditor. In addition, you are missing a forward declaration for QTextEdit in your .h file.

qxoz wrote:

You must include QLineEdit and other which you use #include <QLineEdit>

As long as you just use pointers a forward declaration is sufficient. There is no need to include headers.

Lukas Geyer wrote:

As long as you just use pointers a forward declaration is sufficient. There is no need to include headers.

In fact, in most cases it’s good practice to not include the header where a forward declaration is sufficient. Speeding up compile time is only one of the advantages.

Lukas Geyer wrote:

It is spelled QLineEdit, not QLineEditor. In addition, you are missing a forward declaration for QTextEdit in your .h file.

I think that’s the point. the reason i include qlineedit is it said something is not decleared. there is no include qlineedit on the book.

Samples in books often ommit includes for classes provided by well-known libraries for the sake of brevity. Often, you can download the samples as working source code, and there the needed includes will be there.