[swift-corelibs-dev] IndexPath performance

Tony Parker anthony.parker at apple.com
Tue Aug 2 04:09:16 CDT 2016

Hi Stephan,

Do you have some benchmarks that you could share? That would help us focus performance work in the right area.

I know that 2-item IndexPaths are super common with UIKit collection view and friends, so we may just want to special case those. Unfortunately, NSIndexPath is not abstract, so subclassing it in the same way that we do for a few of the other bridged types (to use native Swift refcounting) is not easy. On the other hand, the ObjC implementation does use tagged pointers, so some NSIndexPaths are really cheap to create.

- Tony

> On Aug 1, 2016, at 11:44 PM, Stephan Tolksdorf via swift-corelibs-dev <swift-corelibs-dev at swift.org> wrote:
> Hi,
> IndexPath is currently implemented using an [Int] array that is bridged to an NSIndexPath only on demand. Since IndexPath values are primarily used together with Objective-C APIs, wouldn't it be better to implement IndexPath directly as an NSIndexPath wrapper, in order to avoid the overhead of temporary array instances?
> - Stephan
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