Rosyna Keller
@gte My beef with people that don't grasp systems programming if they can't imagine how small optimizations in many APIs quickly add up!
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@mjtsai Fast enumeration requires a lot of compiler support and it just happened to be an Objective-C 2.0 feature. https://www.mikeash.com/pyblog/friday-qa-2010-04-16-implementing-fast-enumeration.html …
Marcel Weiher
Michael Tsai
@mjtsai And many of the older classes (NSMenu, NSView, NSWindow, et cetera) have ivars no longer in use.
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@mjtsai In fact, NSWindow got so insane that a new class, NSWindowAuxiliary, was created to hold the additional ivars. -
@mjtsai As NSWindowAuxilary isn't public, Apple can add and remove ivars as needed without having the fragile base class problem. -
@rosyna So why are they still using it now that we have Objective-C 2? - View other replies
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@mjtsai As long as the 32-bit i386 runtime exists, they can't dump the ivars from the headers, sadly. -
@rosyna So, again, this is not (yet) an actual performance improvement resulting from Objective-C 2. -
@mjtsai While NSWindow may have been good to show the pain of fragile base classes, it may have been bad for an optimization example -
@mjtsai a better example would be NSStringDrawing, all the Gesture Recognizer classes, NSIndexPath, various NSCollectionView classes - View other replies
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@rosyna Interesting that they added hash ivar for NSIndexPath. NSStringDrawing is a category so not sure what you are referring to there. - Show more
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@rosyna I kind of doubt removing old ivars from view classes makes up for slowing down every ivar access with extra indirection. -
@rosyna Non-fragile is great for other reasons, but if we're talking about optimization…
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