Address Book constants evaluating as zero

问题

I have a program where for certain code paths, the address book constants (such as kABPersonEmailProperty, kABPersonAddressProperty) evaluate to their normal non-zero value. However, if I follow a different code path, all these constants evaluate to zero.

Furthermore, once I follow the "successful" code path, if I take the problematic code path it works.

Is this some kind of compile linkage issue ?

I could also be over-releasing a variable somewhere.

回答1:

Okay, mystery solved. To Apple's credit, the behavior is documented.

See link text

"Special Considerations: The value of these constants is undefined until one of the following has been called: ABAddressBookCreate, ABPersonCreate, ABGroupCreate."

来源：https://stackoverflow.com/questions/1235131/address-book-constants-evaluating-as-zero