release CFString

Question

I use this code to get the last name of ABPerson

CFStringRef lastNameRef = ABRecordCopyValue((ABRecordRef)personRecordRef, kABPersonLastNameProperty);
NSString *friendLastName = (NSString*)lastNameRef;
CFRelease(lastNameRef);

it work fine when the value of last name is not equal to NULL but when the this value is NULL the application crash at the third line because I try to relese NULL

the question is witch is the best way to releasing the CFString in this case without causing the crash of the application

Answer 1

Just use an if to check for NULL.

if (lastNameRef != NULL)
    CFRelease(lastNameRef);

Answer 2

CFRelease is old C style code. One should check for NULL before calling CFRelease as also set lastNameRef to NULL after calling CFRelease.

if (lastNameRef != NULL) { CFRelease(lastNameRef); lastNameRef = NULL; }

Answer 3

CFRelease expects a non-NULL pointer. You could check for that with an if statement, but it is easier to simply release or autorelease friendLastName instead:

CFStringRef lastNameRef = ABRecordCopyValue((ABRecordRef)personRecordRef, kABPersonLastNameProperty);
NSString *friendLastName = (NSString*)lastNameRef;
// use friendLastName
[friendLastName release];

or

CFStringRef lastNameRef = ABRecordCopyValue((ABRecordRef)personRecordRef, kABPersonLastNameProperty);
NSString *friendLastName = (NSString*)lastNameRef;
[friendLastName autorelease];
// use friendLastName

As you don't seem to use lastNameRef, you could also inline that variable:

NSString *friendLastName = (NSString*)ABRecordCopyValue((ABRecordRef)personRecordRef, kABPersonLastNameProperty);
// use friendLastName
[friendLastName release];

or

NSString *friendLastName = (NSString*)ABRecordCopyValue((ABRecordRef)personRecordRef, kABPersonLastNameProperty);
[friendLastName autorelease];
// use friendLastName