Question

I’m confused with bridge and bridge_transfer, is this correct?

-(void)getData{
    ABAddressBookRef addressBook = ABAddressBookCreate();
    NSArray *allPeople = (__bridge_transfer NSArray*)ABAddressBookCopyArrayOfAllPeople(addressBook);

    NSString *name;
    for ( int i = 0; i < [allPeople count]; i++ )
    {
        name = (__bridge_transfer NSString *) ABRecordCopyValue((__bridge ABRecordRef)[allPeople objectAtIndex:i], kABPersonFirstNameProperty);
    }
    CFRelease(addressBook);
    allPeople = nil;
}

Is there anyone who can explain me how to use them?

Answer 1

If you have automatic-reference-counting (ARC) turned on, the code is correct.

There are two __bridge_transfer in your statements. As a result, the ownership of created CFObjects will be transferred to NSObjects. If you have ARC turned on, they will be freed up automatically. If you used __bridge instead for these 2 statements, you will need to explicitly call CFRelease to release CFObjects created by the *Copy API.

The __bridge statement is also correct. Because you are referencing an NSObject in CF API. You are not transferring ownership, so that ARC will free it up.