The book uses the NSLog in an odd way in a number of places. The way to code the line without warnings is:
NSLog(@"Index is %d",buttonIndex);
When you compile (Build and Run) the program and it runs in the emulator you will notice that the Tasks "stop sign" lights up since it is running in the debugger as well. When you launch it in the simulator it is not running in the debugger. Tasks is dim.