HI, I don't know if it's the right forum to post my question and I apologize if not. I have just bought The definitive guide to learn Macruby and tools to develop some applications. However, I have a problem. page 129, for Actors. In Table View, col. one: I can not edit the cell when I run the program. I open the CoreDataExample and I compare carefully my settings ... without find something ... I am on Mac OS Snow, 10.6.8 and I use Xcode3.2.6 One more thing :) p130, the explanation for choosing another cell class doesn't work: In the identity tab, in class identity field, I can not choose NSButtonCell for example. What I have to do is to drag from class library the NSButtonCell to the cell in my table and the the class identity field is set to NSButtonClass. Maybe it' the right way to do this... I am just a beginner ! Thank you for reply. Have a nice day. François