Hi folks.
For those of you doing work with Objective-C on Cocoa platforms, I want to draw
your attention to a great new idiom. Back in October, David Kilzer added
bridge_cast, a type-safe set of functions that convert an Objective-C pointer
to a Core Foundation pointer or vice versa, preserving types across the
toll-free bridging boundary. It’s better than traditional non-WTF idioms where
you use casts that look like “(__bridge id)” because you don’t have to write
the type, and the correct corresponding type is chosen for you.
When you have a CFStringRef and need to use it as an NSString key and value in
an Objective-C dictionary, for example, the idiom would be:
bridge_cast(constantKey): bridge_cast(constantValue),
Rather than the old:
(__bridge id)constantKey: (__bridge id)constantValue,
It converts to NSString *, not id, which is better for many contexts, and good
here, too. Since the function works in both directions, it will also turn an
NSDictionary into a CFDictionaryRef. And it works on both raw pointers and on
RetainPtr. I find it’s even more welcome to have something that can convert a
RetainPtr<CFDictionaryRef> into RetainPtr<NSDictionary> without danger of
getting the reference counting wrong, doing the right thing in both ARC and
non-ARC source files, and optimizing the move cases appropriately.
Please consider this instead of writing things like (CFStringRef)keyNS.get()
because it’s easier to see it’s correct.
— Darin_______________________________________________
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