I\'m learning iPhone programming from Erica Sadun\'s The iPhone Developer\'s Cookbook. When I run the app I created by following the steps in the Temperature Conversion Exa
As Kevin answered, you will find more helpful debugging info by setting a breakpoint at objc_exception_throw.
If you are using Xcode 4.2, you can add this symbolic breakpoint by going to Breakpoint Navigator > Click on the add icon on the bottom left > Add symbolic breakpoint > Enter objc_exception_throw for Symbol > Done.