I am following along with an example in a book with the code exactly as it is in the example code as well as from the book, and I'm getting an error at runtime. I'll try to describe the life cycle of this variable as good as I can.

I have a controller class with a nested array that is populated with string literals (NSArray of NSArrays, the nested NSArrays initialized with arrayWithObjects: where the objects are all string literals - @"some string"). I access these strings with a helper method added via a category on NSArray (to pull strings out of a nested array). My controller gets a reference to this string and assigns it to a NSString property on a child controller using dot notation. The code looks like this (nestedObjectAtIndexPath is my helper method):

NSString *rowKey = [rowKeys nestedObjectAtIndexPath:indexPath];
controller.keypath = rowKey;

keypath is a synthesized nonatomic, retain property defined in a based class. When I hit a breakpoint in the controller at the above code, the NSString's value is as expected. When I hit the next breakpoint inside the child controller, the object id of the keypath property is the same as before, but instead of showing me the value of the NSString, XCode says that the variable is "out of scope" which is also the error I see in the console. This also happens in another sub-class of the same parent.

I tried googling, and I saw slightly similar cases where people were suggesting this had to do with retain counts. I was under the impression that by using dot notation on a synthesized property, my class would be using an "auto generated accessor" that would be increasing my retain count for me so that I wouldn't have this problem. Could there be any implications because I'm accessing it in a sub-class and the prop is defined in the parent?

I don't see anything in the book's errata about this, but the book is relatively new (Apress - More iPhone 3 Dev). I also have double checked that my code matches the example 100 times.