objective c - Toll free bridges

Question

As a newcomer to iPhone development and Objective-C in general over the last few weeks I have come across numerous mentions of 'Toll free bridges' between CF and NS frameworks.

One particular example would be CFStream and NSStream.

Does a resource exists documenting all of these bridges and how to use them ? Is it just as simple as casting from an object of one type to another ?

I ask as at the moment I am using NSStream calls that are not stricly allowed within the iPhone SDK and understand that I should be using CFStream calls.

EDIT: A useful article about how TFB works

Answer 1

Toll-free bridging means that the data structures are interchangeable. It is just as simple as casting — that's the "toll-free" part. Anyplace you can use the type on one side of the bridge, you can use the other. So, for example, you can create a CFString and then send NSString messages to it, or you can create an NSArray and pass the array to CFArray functions.

Apple keeps a list of the supported toll-free bridged types on its site.