On p. 286, the code mentions those two methods:
[code]- (void)addOwnerNamesObject:(NSString *)n;
- (void)removeOwnerNamesObject:(NSString *)n;[/code]
However, I assume you accidentally used the “…Object” due to code completion.
For other readers, the correct methods should be (as shown in the implementation and on p. 289):
[code]- (void)addOwnerName:(NSString *)n;
- (void)removeOwnerName:(NSString *)n;[/code]