I'm new to Obj-C and when I tried to run my application I got this error in the run log: 2006-04-30 01:01:18.940 MyProject NSScanner: nil string argument I don't really understand what that means because I don't know where in my code the error occurred. Is one of those numbers a line number? XCode's debugger seems really unintuitive. I'm used to eclipse, where if an error occurs you can jump right to the part of your code where the problem is. How can I do this in XCode?