Toll free bridging gotchas

Question

Are there any gotchas for Toll free bridging between NS and CF types?

I'm not sure if I'm doing it wrong but I can't seem to use CF opaque types like ABAddressID inside of an NS Array.

Answer 1

There are not too many 'gotchas'. But this is a C based language, so not every item descends from a CFType. For instance an ABRecordID is really just a 32 bit integer. So its not a CFType. To add ABRecordIDs to an array you would do something like this:

NSMutableArray* newArray = [NSMutableArray array];

ABRecordID someID = 24875247; // you get this somewhere from some call

[newArray addObject:[NSNumber numberWithInt:someID]]; // adds an ABRecordID to the array by putting the int into an NSNumber

Then later when you want the number back:

ABRecordID thatID = [[newArray objectAtIndex:0] intValue]; // retrieve the number, then ask for its int value.

If you read the documentation on a CFType, it will always say whether it is toll free bridged with some NS* counterpart.

Quote from the docs: "CFNumber is “toll-free bridged” with its Cocoa Foundation counterpart, NSNumber. This means that the Core Foundation type is interchangeable in function or method calls with the bridged Foundation object. Therefore, in a method where you see an NSNumber * parameter, you can pass in a CFNumberRef, and in a function where you see a CFNumberRef parameter, you can pass in an NSNumber instance. This fact also applies to concrete subclasses of NSNumber. See Integrating Carbon and Cocoa in Your Application for more information on toll-free bridging."

But an int in C is most definitely NOT a CFNumber.

Hope that helps,

--Tom