Do I need to manually release CFStringRef?

Question

Can you please tell me which is the right way and why in non ARC world.

+ (NSString *)getUUID {
CFUUIDRef theUUID = CFUUIDCreate(NULL);
CFStringRef string = CFUUIDCreateString(NULL, theUUID);
CFRelease(theUUID);
return [(NSString*) string autorelease];
}

or

+ (NSString *)getUUID {
CFUUIDRef theUUID = CFUUIDCreate(NULL);
CFStringRef string = CFUUIDCreateString(NULL, theUUID);
CFRelease(theUUID);
return (NSString*)string;
}

Answer 1

The other answers are correct for manual retain counting. When you come to your senses ;^) and switch to ARC, you won't be able to send autorelease. Instead, under ARC, do it this way:

+ (NSString *)getUUID {
    CFUUIDRef theUUID = CFUUIDCreate(NULL);
    CFStringRef string = CFUUIDCreateString(NULL, theUUID);
    CFRelease(theUUID);
    return CFBridgingRelease(string);
}

A CFBridgingRelease is equivalent to a CFRelease for the purposes of balancing the +1 retain count returned by CFUUIDCreateString, but also returns a still-valid reference that ARC will take care of releasing.

Answer 2

CFStrings do need to be released. The first way is correct because CFString is toll-free bridged with NSString, and thus can safely be autoreleased like an NSString.