Boost - Core Foundation

I have started plumbing in some of Core Foundation into Cello. Core Foundation objects are owner-counted which leaves you to take care of calling CFRetain and CFRelease at appropriate moments. It is very straight forward except that adding all of the CFRetain and CFRelease clutters your code and (more importantly) can be tricky to get right - it is really easy to forget a release, especially if you consider exceptions. .

Things are eased a little if you have classes that wrap some of the Core Foundation objects - but the thing that really makes the difference is smart pointers.

In a previous life I used Apple Class Suites (ACS) which was a part of MacApp. ACS wrapped most of the underlying OS APIs in good C++ and introduced me to using smart pointers that would automatically call CFRetain and CFRelease. So if you wanted a pointer to a CFString that would automatically call CFRelease when it went out of scope there was an AutoCFString_AC smart pointer.

There is excellent support for smart pointers in boost. Declaring and implementing a smart pointer using intrusive_ptr to do the same as MacApp's AutoCFString_AC takes just three lines of code in boost:

 typedef boost::intrusive_ptr auto_CFString;
inline void intrusive_ptr_add_ref(CFStringRef p)
   { ::CFRetain(p); }
inline void intrusive_ptr_release(CFStringRef p)
   { ::CFRelease(p); }

For those curious in the MacApp annex of history, MacApp though 'dodo dead' has played an important part in the development of many application arameworks, there is an insightful article in wikipedia here .