Casting an NSObject to NSString

I believe this will do what you need:

NSLog(@"lowerCaseString is: %@", [(NSString *)object lowercaseString]);

Note I just added a * to your second line of code to make a pointer to NSString.

Why is object declared as an NSObject if it's supposed to be an NSString? If you intend to call NSString methods on it, declare it as an NSString or leave it as an id. Then you won't get errors.