Many thanks to all who responded. Here's a few resolutions for the archives:
1. CFType: cast to id and autorelease. Verdict: it is OK (under manual memory management). http://www.cocoabuilder.com/archive/cocoa/215004-autorelease-cgimageref.html http://developer.apple.com/library/mac/#documentation/CoreFoundation/Conceptual/CFDesignConcepts/Articles/tollFreeBridgedTypes.html Sending an autorelease to an object or opaque type puts the pointer into a collection that will later receive a release call. CFType can be released. (This has worked for me in practice for quite some time, but I'm looking to move to ARC for a new project). 2. Returning an autoreleased opaque type under ARC. Verdict: Might not even make sense. Mike Ash's excellent explanations did help clarify things, but in the end, I'm not sure that my original request is even sensible. I was looking to hand over an opaque type that was in some collection scheduled to get released later. I don't think any of the casting annotations amount to this. Mike's only example of bridging in this direction (toward a CFType) was the __bridge_retained to transfer ownership from the system into our hands, which is where I was in the first place returning the CGColor. 3. What to do? Keep it simple: I'll modify the method name to reflect the need to memory manage the return value - CGImageCopy. Here is the final method: - (CGColorRef)CGColorCopy { NSColor *colorRGB = [self colorUsingColorSpaceName:NSCalibratedRGBColorSpace]; CGFloat components[4]; [colorRGB getRed:&components[0] green:&components[1] blue:&components[2] alpha:&components[3]]; CGColorSpaceRef theColorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB); CGColorRef theColor = CGColorCreate(theColorSpace, components); CGColorSpaceRelease(theColorSpace); return theColor; } Thanks for everyone's input! John On Oct 19, 2011, at 10:09 AM, John Joyce wrote: > Check the nice clear tutorial at > http://www.mikeash.com/pyblog/friday-qa-2011-09-30-automatic-reference-counting.html > It spells out how to handle CF types in ARC. > > On Oct 19, 2011, at 9:52 AM, Wade Tregaskis wrote: > >>> Following Cocoa convention you'd want to cast it to what and autorelease >>> it? CGColorRef isn't toll-free bridged with anything. If you have been >>> casting it to id and autoreleasing it you might have gotten away with that >>> before but I don't think it's documented anywhere you can do that with >>> CFTypes in general. >> >> You can. It may not be in the docs, but all CF types are also NSObjects (or >> a subclass thereof). >> >>> You could change the semantics of the method to return a CFRetain()ed >>> object and make it the responsibility of the caller to release it (and >>> change the name of the method too to make it clear) or you can create a >>> UIColor with your CGColorRef, then CFRelease() it and return the UIColor. >>> >>> Mixing autorelease and CFTypes does't seem like a great idea, but I'm >>> prepared for someone to point out a whole piece of documentation I've never >>> seen, that often seems to happen! >> >> No, mixing them is indeed a bad idea. CF doesn't have auto release pools, >> so anything dealing with CF types is free to not think about them, and in >> practice often does. I would go with explicitly returning the CGColorRef >> retained. >> _______________________________________________ > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
